CHITONIDiE. 345 



ONiTHOCHiTON, GraJ^ Insertion-plates regular, flat behind ; 

 anterior valve with many slits, middle with one, posterior with 

 none ; teeth serrate ; eaves deeply furrowed ; sinus moderate, 

 lobed ; girdle with chaffy hairs. G. Lyellii, Sowb. (Ixxxvi, 82). 



PLACiPHORA, Gray. Insertion-plates regular, ribbed behind ; 

 anterior valve with many slits, middle with one, posterior with 

 none ; teeth slightly propped ; eaves small ; sinus small ; girdle 

 hairj', with regular pore-tufts. C. Carmicliaelin, Gray. 



FREMBLYA, H. Adams. Valves regular, ribbed behind ; the 

 middle with one, anterior with many, posterior with no slits ; 

 teeth exeurved ; eaves small ; sinus broad, shallow ; girdle hairy, 

 with regular pore-tufts. Distinguished by its exeurved teeth. 

 C. Gollei, H. Ad. 



EUPLAciPHORA, Shutt. Sinus wide, planate ; girdle set with 

 bristles, not fasciculated. 



GUiLDiNGiA, Cpr. Yalves partly immersed ; girdle emar- 

 ginate behind. G. petholatus^ Sowb. (Ixxxvi, 89). 



G. Mopaloidea. 



Tail-valve with posterior sinus and one slit on each side. 



MOPALIA, Gray. Shell regular ; laminae lengthened ; anterior 

 valve with six or more slits, the others with a single slit ; last 

 valve sinuate behind ; sinus narrow ; mucro median, depressed ; 

 sutures indented; girdle wide, bristly, sometimes fissured be- 

 hind, sometimes projecting anteriorly. G. Blainvillei, Brod. 

 (Ixxxvi, 90). 



PLACiPHORELLA, Cpr. The hairs or part of them issuing in 

 fasciculi from sutural pores. G. velata, Cpr. 



KATHERiNA, Gray. Armor small ; girdle smooth, much ex- 

 panded in the sutures ; laminae greatly projecting anteriorly, the 

 posterior valve lobate ; sinus deep, spongy. Branchiae encircling. 

 Distr. — G. tunicatuK^ Wood (Ixxxvi, 91). W. Coast America, 

 California to Alaska, Kamtchatka. 



ACANTHOCHiTON, Lcach. lusertion-platcs thrown forward, 

 laminated ; anterior valve with five slits, middle and posterior 

 valves each one ; teeth long, sharp, smooth ; eaves small ; gills 

 median; sinus deep, broad, spong}'' ; girdle hairy, with long, fas- 

 ciculated spiculse. G.fascicularis, Auct. 



MACANDRELLUS, Cpr. Valves partly immersed ; mucro Isch- 

 noidal ; posterior lamina rugosely lobate ; lateral area depressed. 

 G. plumens, Cpr. 



STECTOPLAX, Cpr. Valves two-thirds immersed. 



NOTOPLAX, H. Adams. Tail-plate crenate behind ; first valve 

 with five, last with two, middle with one slit ; teeth crenate, sharp, 

 smooth ; eaves minute ; sinus deep, narrow ; gills crowded with 

 spicules, and with sutural pores. 



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