We consider Cerithiopsis vanhyningi Bartsch, 1918 to be a junior synonym of C. fusiformis (C. B. Adams, 1850) based upon the following research. Bartsch’s C. vanhyningi is distinguished from C. fusiformis  principally based on C. vanhyningi having “the first (postnuclear whorl) marked by two slender spiral cords…” Bartsch also indicates that "Beginning with the second postnuclear whorl, a slender thread makes its appearance ... a little nearer to the posterior than the anterior; in fact, it is so close to the posterior that the nodules on the later turns (whorls) have a dumb bell shaped aspect." This description fits the "fused" nature of the two upper spirals characteristic of the second through fifth teleoconch whorls of C. fusiformis.  So, the key difference between the two was thought to be the number of spirals on the first teleoconch whorl - two on C. vanhyningi and three on C. fusiformis.

Rolán and Espinosa (1995) discussed C. vanhyningi after examining the holotype and two paratypes at the National Museum of Natural History, Washington. They found the holotype lacking nuclear whorls and the paratypes in poor condition. They did not comment regarding the number of spirals on the first teleoconch whorl. They did comment that "on C. vanhyningi they (upper two rows of nodules) are almost fused" and that "C. fusiformis has the two upper cords on the teleoconch close but separated." However, this comment about C. fusiformis was inconsistent with their description of C. fusiformis after having examined the holotype, where they indicated "Moreover, there are three nodulous cords crossed by axial ribs at the beginning of the teleoconch, but on subsequent whorls there are only two, as the upper cords become fused. (emphasis added) They separate on the fifth or sixth whorl..." Rolán and Espinosa apparently did not closely examing for spiral counts on the first teleoconch whorls of the type material of C. vanhyningi, or the shells were in too poor condition. So, apparently, they did not consider the possibility that C. vanhyningi and C. fusiformis might be the same.

Initially, back in the late 90’s when I was just starting to become aware of micro-shells, doing field collecting for researchers, and being tutored by Harry Lee, I sent a lot of shells I had tentatively identified as C. vanhyningi, to Harry for confirmation. (Note: I had not been sufficiently observant to distinguish three spirals in the first teleoconch whorl.) He commented that the shells in question were C. fusiformis and that he suspected C. vanhyningi was an invalid junior synonym. He referred to Rolán and Espinosa (1995) and their observation that the holotype of C. fusiformis revealed that “there are three nodulous cords … at the beginning of the teleoconch” and that the “fusing” of the two upper cords does not occur until subsequent whorls. This was consistent with his examination of the C. vanhyningi paratypes deposited at the Florida Museum of Natural History (FLMNH). Harry reported that he had recently visited the FLMNH to examine this paratype material and found the Florida shells he and I had been tentatively identifying as C. vanhyningi or C. fusiformis to be:

“Identical to all nine paratypes of C. vanhyningi Bartsch, 1918 (UF 10153).” “Bartsch (1918) and Rolán and Espinosa (1996) believed the initial postnuclear whorls of C. vanhyningi to have postnuclear nodules fused, but all nine paratypes have three spirals initially distinct; the posterior spiral then approximates (fuses with in most instances) middle one…” “We must therefore synonymize C. vanhyningi with C. fusiformis …”

Harry’s examination of the FLMNH paratype material revealed that Bartsch’s description of C. vanhyningi as “the first (postnuclear whorl) marked by two slender spiral cords…” was in error (Bartsch and I apparently made the same observational error). Rolán and Espinosa’s examination of the holotype of C. vanhyningi , which “lacked nuclear whorls,” and two paratypes that “are in poor condition” failed to discern whether there were two or three cords on the first postnuclear whorls.

So, with Harry’s explanation we have synonymized C. vanhyningi. Harry also addresses this issue in his recent book Marine Shells of Northeast Florida 2009 (see #417) and subsequently in Rolán, Lee, Krisberg and Fernández-Garcés (2012).

References:

Lee, Harry G. 2009 Marine Shells of Northeast Florida. Jacksonville Shell Club, Jacksonville, Florida.

Rolán, E. and Espinosa, J. 1995. The family Cerithiopsidae (Mollusca: Gastropoda) in Cuba 3. The genus Cerithiopsis s. l., species with brown shells. IBERUS, 13(2): 129-147.

Rolán, E., Lee H., Krisberg, M. & Fernández-Garcés, R. 2012. The Protoconch and Early Teleoconch Whorls of the Brownish Cerithiopsis (Mollusca, Cerithiopsidae) in the Caribbean and Adjacent Regions. Xenophora 139:11-16.