BY E. M. JOHNSTON, P.L.S. 



97 



G-enus Patella. (418-424) 

 Shell conical, more or less depressed, oval at the base ; apex sub- 

 central or anterior, from which usually radiate ribs, 

 which are are frequently nodose ; mostly crenulated 

 on the inner margin. Dist. — World-wide. (Common 

 Limpet.) 



(Euplacifoka. Gray.) 

 pores, beset with bifurcate 



(li.) Family Chitonidje. 

 Shell composed of eight separate transverse imbricating plates, 

 lodged in a coriaceous mantle, which forms an 

 expanded margin around them. 



G-enus Chiton. Linn. (425-433.) 

 Same general description as given for the family. 



Sub-Genus Chiton. Lam. 



Girdle covered with distinct scales ; anterior and posterior 



valve with many slits, middle valve with one. 



Sub-Genus Lophybtts. Poli. (Badsia. Gray.) 



Teeth in middle valve two or more ; differs also from Chiton 



in having side slits. 



Sub-Genus Lepidopleitbus. Eisso. (Isnochiton.) 

 Scales transverse, flattened, somewhat imbricated, generally 

 striated. 



Sub-Genus Plaxifhoba. Gray. 

 •Mantle with a double series of 



bristles, one row at the insertion of the valves, the 

 other at the external margin ; shell with the valves 

 broad, transverse, external. 



Sub-Genus Acanthocites. Eisso. 

 -Mantle densely spinulose, surrounded with a scries of 

 setigerous pores ; shell with the valves deeply 

 immersed, sub- equal externally, the exposed part 

 moderate ; cordate as broad as long ; plate of insertion 

 of the anterior valve six lobed, that of the middle bi- 

 lobed, that of the posterior five lobed, 

 Genus Chitonellus. Blainville. (434-435.) 

 ai l plate funnel shaped ; laminae thrown forward ; insertion 

 plates very sagittate; slits in anterior valve 5, in 

 middle 0-1, in posterior none ; teeth very short, except 

 of sutures; eaves distinct; sinus very deep and 

 narrow ; girdle crowded with bristles, no tufts ; gills 

 posterior. 



-jvjp Sub-Genus Cbyptoplax. 



Middle valve without ribs; girdle 

 tufted. 



Gray, 

 with crowded 



bristles, 



G 



