ON 7 MOLLUSCA OF THE \\EST COAST OF NORTH AMERICA. 



619 



220. Acantliopleura scabra, Eve. = Californicus, Nutt. Insertion-plates resemble 



Katherina. Valves with, coarse V-shaped ribs, and projecting beaks. 



221. Acanthopleurafluxa, n. s. Green, mottled with orange-red ; not beaked j with 



only marginal and diagonal ribs. 



222. Ischnochiton Magdalensis,ttds. Large, strong- valved, typical. Sculpture much 



fainter than in southern shells. Mantle-margin wilh striated scales like 

 flattened bristles. Side plates 2- or 3-lobed. Beach-20 fm. Cp. 



223. I-chnochiton veredentiens, n. s. Margin similar. Small, arched, sculptured 



like Mertensii, but with 2 rows of bosses, one of which dentates the sutures. 

 10-20 fm. Cp. 



224. Lepidopleurus regularis, Cpr. P. Z. S. 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. s. Small, arched, orange : rows of prominent 



granules over shagreened surface. Lobes blunt, slightly rugulose, close to 

 eaves. 8-20 fm. Op. 



226. Lepidopleurus pectinatus, n. 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. Trachyderrnon retiporosus, n. s. Subgenus of Ischnochiton : mantle-scales very 



small, close, smooth. Sp. like scrobiculatus, 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. [ Trachydermon dentiens, Gld. E.E. No shell known answering to diagnosis and 



figure.] The 4 following species have incisors blunt, eaves not projecting. 

 231 b. Trachydermon pseudodenticns=t\-pe 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 Harhceaii, Cpr. P. Z. S. 1855, p/231. Large, arched. Inside 



callous, without rows of punctures to slits : eaves spongy. 



234. Trachydermon Nuttallii, Cpr. P. Z. S. 1855, p. 231. Large^plain, flat. Incisors 



slightly rugulose : eaves spongy. 



235. Trachydermon flectens, n. s. Mantle-margin scarcely granular. Rosy, very 



small, scarcely sculptured: valves beaked and waved as in M, Simpsomii 

 eaves and incisors normal. 



135 



