ON MOLLUSCA OF THE WEST COAST OF NORTH AMERICA. 649 
Nutt.) Jew. | B. A. | Smiths. Ins. Ken. | Lord.|Swan.| Cooper. 
220. Acanthopleura scabra....) M | — | C ET P|—|— I 
221. FUT BIB ta crave star yee otece —|—)}— — =|— I 
222, Ischnochiton Magdalensis | — | — | L LM | —}]—j|— DI 
223. veredentiens ...... —|—}— — —|—|— I 
224, Lepidopleurus regularis ..| — | — | C — —|—|— _ 
225. scabricostatus...... ;—}|—|/—]| — —|—)|— I 
226. Cen ALU Se Jicliaiens —|—|— |; — —}|—)|— I 
227. —— Mertensii.......... }—;<=|/C |] M Pair saly WV. — 
228. Trachydermon retiporosus. — | — | —| — P|—j|— _— 
229, —— interstinctus ...... —!;=|P — —|—|/— — 
230. PEMIAUS:| eres .)e's. eo —|/—|;—|} — P|—)— — 
231. dentiens .......... —|;—/|P/ — —|-—/|—- — 
2316, —— pseudodentiens ..) — | — | — _— Bil Mil D 
232. Gothicus.......... 2) 2 —|/—|— I 
233. —— Hartwegii ........ |} — |= © iP —|-—-|— — 
234. —— Nuttallii.......... M/—/|C] M —|—|V I 
235. HE CEOTSH) Fs\ce-0ivhech Y ;}—}|—}|— M Po Viel == D 
220. Acanthopleura scabra, Rve. = Californicus, Nutt. Insertion-plates resemble 
Katherina, Valves with coarse V-shaped ribs, and projecting beaks. 
221. Acanthopleura fluxa,n.s. Green, mottled with orange-red ; not beaked ; with 
only marginal and diagonal ribs. 
222. Ischnochiton Magdalensis, Hds. Large, strong-valved, typical. Sculpture much 
fainter than in southern shells. Mantle-margin with striated scales like 
flattened bristles. Side plates 2- or 3-lobed. Beach—20 fm. Cp. 
223. Ischnochiton veredentiens, n.s. Margin similar. Small, arched, sculptured 
like Mertensti, but with 2 rows of bosses, one of which dentates the sutures. 
10-20 fm. Cp. 
224, Lepidopleurus regularis, Cpr. P. Z. 8. 1855, p. 232. Subgenus of Ischnochiton : 
mantle-scales Lophyroid, generally striated. Sp. arched, green, shagreened. 
Side lobes 2-4: eaves spongy, not projecting. 
225. Lepidopleurus scabricostatus, n. 8. Small, arched, orange: rows of prominent 
granules over shagreened surface. Lobes blunt, slightly rugulose, close to 
eaves, 8-20 fm. Cp. 
226. Lepidopleurus pectinatus, u.s. Olive: strong sculpture over shagreened surface: 
side areas ribbed: outer margin and inner sutures pectinated. Bch. Cp. 
227. Lepidopleurus Mertensii, Midd. Red: highly sculptured over smooth surface : 
side areas with rows of bosses. Mantle-scales smooth, rounded. 
228. Trachydermon retiporosus,n.s. Subgenus of Ischnochiton: mantle-scales very 
small, close, smooth. Sp. like scrobrewatus, central pattern in network, 3-6 
side ribs. 
229. Trachydermon interstinctus, Gld. E.E. Centre minutely punctured : 6-8 blunt 
side ribs. 
230. Trachydermon trifidus,n.s. Centre-punctures few, deep: 2-4 blunt ribs: side 
plates with 2 slits. 
231. [Zrachydermon dentiens, Gld. E.E. No shell known answering to diagnosis and 
figure.] The 4 following species have incisors blunt, eaves not projecting. 
2316. Trachydermon pseudodentiens=type specimen of dentiens. False appearance of 
teeth due to colour or ridges of growth. Closely granular : areas indistinct. 
Sinus broad, squared: eaves spongy. 
232. Trachydermon Gothicus, n.s. Blunt parallel riblets along very arched back. 
Sutural lobes united at sinus: eaves not spongy. 8-20 fm. Cp. 
233, Trachydermon Hartwegii, Cpr. P. Z.S. 1855, p. 231. Large, arched. Inside 
callous, without rows of punctures to slits: eaves spongy. 
234, Trachydermon Nuttallit, Cpr. P. Z. 8. 1855, p. 231. Large, plain, flat. Incisors 
slightly rugulose : eaves spongy. 
235. Trachydermon flectens, n.s. Mantle-margin scarcely granular. Rosy, ver 
small, scarcely sculptured: valves beaked and waved as in M. Stimpsoniv: 
eaves and incisors normal. 
