322 MAZATLAN UNIVALVES 
Hab.— Panama; common in the sand; C. B. Adams.— 
Mazatlan ; 14 sp. off Spondylus &e. ; L’pool Col. 
Tablet 1526 contains 5 specimens in different states. 
* 369. Cucum cLarHRatuM, x. s. 
C. (Anellum) t. haud parvd, solidiore, annulis valde distanti- 
bus, acutioribus, validis, extantibus, cincté ; interstitiis concavis: 
septo subplanato, mucronato ; in adulta margine laterali haud 
monstrante ; mucrone minima, obtusa, pene in dorsum sité : 
operculo ?...., 
This extremely elegant species is remarkable for its size; 
very distant bar-like rings, which are rather sharp ; gracefully 
curved interspaces ; and nearly flat plug with a scarcely pro- 
minent obtuse mucro, searcely (if at all) inclined to the right. 
Only 12 specimens were found. The youngest sp. measures 
long. ‘057, lat. "007 —017. The largest, long. °102, lat. (inter- 
stices) ‘026, (outside) *03. 
Hab.—Mazatlan ; off Spondylus, extremely rare; L’pool Col. 
Tablet 1528 contains 4 specimens of different ages. 
3/0. CHCUM QUADRATUM, 72. S. 
C. (Anellum) t. parva, curtd, solidd, annulis quadratis xi.— 
xx. cincti; interstitiis profundis, quadratis ; apertura sub- 
contractd, annulis coneurrentibus ; septo mucronato, margine 
laterali concavo, mucrone parva, extante, angusta, subdextrorsum 
sité: operculo valde concavo, anfr. circiter x. lined spiralt 
EXPPESSE. 
?Var. compactwum, ¢. interstitiis parvis seu evanidis, annulis 
maxime planatis. 
‘Bhe extreme forms of this shell are singularly different ; at 
one end of the scale being a larger shell, muricated with 
squarish distant rings, passing into C. clathratum; at the 
other, a small stunted state in which the rings have so run 
together that the interstices appear like simple grooves, and 
the shell approaches the young of C. subimpressum. Among 
43 specimens found, however, (of which 3 possessed opercula,) 
there appeared too gradual a transition to allow of their separ- 
ation. At the same time the habit of growth appears quite 
distinct from that of any of the neighbouring species. It is 
customary for Anella to make their rings compact in the mature 
a 
