CLASS GASTROPODA 
19 
Cavolina occidentalis Dali, 1908 
Bulletin, Museum of Comparative Zoology, 43:233, No. 6; PI. 12, fig. 1. 
The “appareil de fermatllre ,, consists of a tooth-like process projecting 
on each side from the ventral plate and entering a depression in the inner 
side of the dorsal plate. The ventral lip is strongly constricted close to 
its narrowly reflected anterior margin. The posterior median spine is 
usually decollate at the tip. The back has a broad median and two nar¬ 
rower lateral obscure ridges ending at the thickened “bridle” or concentric 
callous ridge characteristic of this species; the ventral plate is most convex 
in front, where it is suddenly constricted; the portion near the aperture 
strongly marked by concentric whitish impressed lines with wider inter¬ 
spaces, though these do not interrupt the smoothness of the surface. The 
“hood” or produced margin of the dorsal plate, instead of being produced 
in a nearly continuous plate as figured by Boas for C. tridentata ( telemus ), 
is bent ventrally in a curved manner over the aperture, and about half 
the anterior convexity of the ventral plate is thus overshadowed. The 
whole shell is shorter and more globose than the Mediterranean form as 
figured by Boas, and the lateral slit behind the interlocking processes forms 
a straight, even line, not arcuate and anteriorly expanding, as in the 
figures referred to. The fully adult shell measures 9 mm. long, 6 mm. in 
greatest width, and 5 mm. in greatest convexity. (Dali.) 
Type in United States National Museum, No. 110591. Type locality, 
Northeast Pacific between latitudes 30° and 54° N. 
Range. Northeast Pacific. 
Genus CLIO Linnaeus, 1767 
Shell pyramidal, three-sided, striated transversely; ventral side flat, 
dorsal keeled; aperture simple, triangular, with the angles produced; apex 
acute. (Tryon, Structural and Systematic Conchology.) 
Type. Clio pyramidata Linnaeus. 
Distribution. Atlantic, Mediterranean, Indian Ocean, Pacific, Cape 
Horn. Fossil: Miocene—Britain. 
Clio exacuta Gould, 1852 
Mollusca and Shells of the United States Exploring Expedition (under Wilkes), 488; 
PI. 51, fig. 605. 
T. pellucida, triangularis, subtus concava, supra per convexa antice, 
rotundata, postice valde acuminata, lateribus concaviter arcuatis. Animal 
cervice longo et aliis divergentibus oblongo-ovalibus instructus. (Gould.) 
The shell is an equilateral, spherical triangle, the base convexly rounded, 
and the sides concavely excavated, producing thus a long acute caudal 
