MAZATLAN UNIVALVES 427 
Genus CHEMNITZIA, D’Orb. 
Nat. Hist. Canar. 1839.—Forbes &§ Hanl. Br. Moll. vol. ui. 
— Woodw. Man. Moll. p. 126. 
Turbonilla, Risso, Nat. Hist. Hur. Mer. vol. iv. p. 224, 1826.— 
Phil. Handb. Conch. p.193.—H. & A. Ad. Gen. vol. 1. p. 280. 
Parthenia, Lowe, Ann. Mag. Nat. Hist. vol. vi. p. 511, 1841. 
Pyrgiscus, Phil. Arch. f. Nat. vol. i. p. 50, 1841. 
Pyramis+Jaminea, Brown, Brit. Conch. 
Amoura, Mill. 
Orthostelis, Arad. § Maggy. Cat, Reg. p. 189, ? 1844. 
Species typica. Anfractibus planatis. 
Section A. Without spiral sculpture. 
(a.) Ribs interrupted at the periphery. 
518. Cuemnirzis ? Panamensis, C. B. Ad. 
Pan. Shells, no. 227, pp. 168, 312. 
Tablet 1989 contains a dead specimen which appears suf- 
ficiently like the type in Mr. Cuming’s Collection. It has 5 
whirls, the apex being deficient both in this and in the type. 
The species is rather broad, with very flat whirls, stout, rather 
slanting ribs, and very deeply cut grooves as far as the peri- 
phery. It measures long. °075, lat. °025. 
Hab—Panama; 11 sp. in the sand on the reef, between high 
water and half tide levels; C. B. Adams.—? Mazatlan ; 1 sp. 
off Chama; L’pool Col. 
519. Cuemnitzia C-B-Apamstt, 7. s. 
Ch. t. gracili, alba, elongatd ; vertice nucleoso anfr. Wi 
prominentibus, declivi, marginibus spire rectis swperante ; 
anfr. ii. prope apicem rotundatis ; deinde vii. planatis, suturad 
impressa; liris circiter xviii. rectis, solidis, obtusis, ad peri- 
pheriam subito obsoletis; bast subrotundaté ; labro tenui ; 
columella tenwi, viz intorta. 
Shell intermediate between Ch. aculeus and Ch. Panamensis, 
with all the whirls except those next the apex flattened. The 
apex is very large, with 3 tumid whirls, set rather slanting on 
the axis. It is named in remembrance of Prof. Adams of 
Amherst, U. 8. whose early death has deprived science of one 
