CERION, GROUP XI. 251 



Strongly ribbed, witli 17 to 26 ribs on the penultimate whorl. 

 Aperture small, dark within ; peristome hardly expanded, the margins 

 thin, built forward, becoming free in front, rugose outside. Teeth as 

 in C. ritchiei. 



Length 27, diam. 11^, longest axis of aperture 9^ mill, (form 

 No. 2). 



Length 33, diam. 15, longest axis of aperture 10^ mill, (typical 

 form). 



Length 29^, diam. 14^, longest axis of aperture 10 mill, (form 

 No. 1). 



Highborn Key, on a steep conical hill at the northern end of the 

 key, terminating the range of hills along the eastern side, chiefly on 

 stems of white-barked wild fig trees. 



Distinguished chiefly by the thin margins of the peristome, which 

 is more or less built forward, beyond the ventral outline of the shell. 

 The typical form (pi. 39, figs. 93, 94) measures from 26 to 35 mill, 

 long (type specimen 31^xl3f mill.), and is found abundantly at the 

 place mentioned above. At the base of the same hill on its western 

 side a shorter, wider form occurs (fig. 95), which Mr. Maynard calls 

 form No. 1. Form No. 2 (fig. 96) is smaller, with less produced 

 peristome. It occurs on the flats near the northern bay of the key. 

 Form No. 3 is short, thick and cylindrical, and occurred near the 

 ruins of the house on top of a hill midway of the eastern arm of the 

 key, adjoining the range of typical C. ritchiei. 



Form giganteum (Maynard) is very large, white or copiously 

 stained with dull reddish-brown in the intervals. The size varies from 

 41|xl5 to 33x131 mill. The white form lives in the thickets grow- 

 ing along the hillside to the south of the ruined house mentioned 

 aboved ; the mottled form (pi. 39, fig. 1) is found in a little valley 

 on the hillside near the landing, near the head of the southern bay. 

 It is rather absurd to distinguish this form from typical ritchiei, which 

 occurs in the same area. 



Form pumilum (Maynard). Quite small, with 9-9^ whorls, white, 

 bearing separated ribs, about 18 on the penult whorl. Peristome 

 thin or somewhat thickened, not produced forward above. Length 

 23-24, diam. 11 mill. (fig. 97). About 50 specimens were found by 

 Mr. Maynard clinging to the stems" of two or three small trees, grow- 

 ing just south of a deep gorge making in from the sea, about midway 

 of the western border of the key. 



