MAZATLAN UNIVALVES 483 



seu rarius virescente ; superne conspicue angulato, carina tuher- 

 culosd ; tuherculis plerumque viii. compressis, plus minusve 

 conspicuis, costis radiantihus, scepe suhobsoletis, convenientibus; 

 lirulis spiralibus covfertis, supra carinam mimis conspicuis, 

 rotundatis, sqtiamosis cinctd, quarum interdum iii. ivfra carinam 

 majores, quasi carinulce, sqxiamis majoribzts tiibercidis conveni- 

 entibus ; squamulis lirulanim confertissimis, acutioribus, arcua- 

 tis, labrum actihim crenulantibus ; labia simplici, hand extante ; 

 canali elongatd, oi:)ertd ; costd _2)?«5 minusve coniortd, rimam 

 umbilicalem sapeformante : operculo pyriformi, arcuaio, nigra- 

 rvfescente ; margine tenui, diaphano, intus rubra Uncto ; cicatr. 

 muse, lineis incrementi paucis irregulariter cancentricis. 



The figures of Blainv. and Kien., drawn from a supposed 

 unique specimen, represent the usual state of this pretty little 

 species much better than that of Eeeve Tvhich (if the same 

 species) is an aberrant form.* The shell varies extremely in 

 shape and strength of sculpture, but presents a general lozenge 

 outline from the keel which is always conspicuous. Whether 

 the secondary keels are developed on the basal part of the whirl, 

 depends on the individual, and is rarely the case in young shells. 

 Almost all the numerous specimens were copiously encrusted 

 with coralline, so that the beautiful markings are rarely seen 

 except near the mouth. The largest of the specimens mea- 

 sures long. 1'28, long. spir. '6, lat. "88, div. 60°. 

 A young acuminated sp. 

 A depressed sp, „ 



^a&.— Mazatlan, Batta.—(P. diadema) Payta ; on the reefs : 

 Cuming. — Mazatlan ; common ; L'pool Col. 



Tablet 2262 contains 6 sp. basal keels developed, spire ele- 

 vated.— 2263, 5 do, less elevated.— 2264, 5 do. depressed.— 2265, 

 5 do. basal keels scarcely marked.— 2266, 5 sp. base plain, much 

 depressed.— 2267, 6 do. less depressed. — 2268, 4 do. acumi- 

 nated. — 2269, 6 sp. shewing the lip in different stages of growth. 

 — 2270, 3 do. mouth highly coloured. — 2271, 1 do. canal twice 

 formed. — 2272, 2 sp. miieh iucrusted.— 2273, 3 sp. adhesions 

 incommoding the mouth.— 2274, 4 sp. mended after fracture.^ 

 2275, 1 sp. curiously worm-eaten.— 2276, 8 normal opercula.— 

 2277, 4 do. somewhat irregular ; one with nucleus subcentral. 



• Perhaps the tickets of the types in JIus. Ciimiug hare been displaced. 

 Reeve gives the shell as S. American : but the "Ouma diadema, Xam." of the 

 collection is ticketed "Mauritius," and is certainly distinct from the Mazatlan 

 shell. Tlie latter more nearly resembles C. calcar, Brod, in the collection. 



