"Cerion chaplini new species Figs. 1 to 4.
Shell cylindroid; elongate; solid; rimate. Type of 12 ¼ flat-sided whorls; first 2 ½ whorls amber colored. Suture pronounced. Short parietal tooth or none, and oblique columellar fold. Smooth, or irregularly spaced, distant coastae which parallel growth lines; costae of indifferent strength but well pronounced on the base (interval between costae varying from ½ to 1 ½ mm. behind the peristome of the type). Internal apertural color white through pink to pale violet. Shell weakly mottled with light brown. Costae polished, interstices dull.
Height 39.2 mm., diam. 14.4 mm., 12 ¼ whorls. (Type.)
Height 40.0 mm., diam. 14.8 mm., 12 ¾ whorls. (Largest.)
Height 31.9 mm., diam. 12.5 mm., 10 ¾ whorls. (Smallest.)
Type and 34 paratypes collected by C. G. Chaplin on palm trees inside the mangrove fringe along the north shore of Cayo Largo (station 19). ANSP 186182.
Six immature shells of 7 to 9 whorls were found. These each have a distinct columellar fold. One specimen of 7 ¼ whorls has two pronounced, tubercle-like, parietal teeth ¼ whorl within the aperture. The others either lack these or they are too deeply seated to be seen. The bases of the immature shells are irregularly and intermittently spirally striate. This striation is due to depositions of callus that are visually evident in coloring, but are not raised above their interstices and cannot, therefore, be interpreted as lamellae.
Stations 4a, 5, 13, 15a, 19 (type locality) and 24.
The single specimen collected by Chaplin at Station 4a was inhabited by a hermit crab. Excepting station 19 the other Cayo Largo stations where this species was found produced only two or three empty shells that had probably been dropped by hermit crabs. From the number of shells found at station 13 it is evident that the species is also established on Cayo de la Piedra. it was not found on the three Majas islands.
This species is near both Cerion iostomum (Pfr.) and C. hyperlissum Pils. and Van. It differs from the former primarily in being elongate and is lacking the pronounced violet coloration within the aperture. It differs from C. hyperlissum primarily in the lack of the deeply penetrating parietal tooth."
