122 ISCHNOCHITON. 



I. VEREDENTIENS Carpenter. Un figured. 



Shell small, whitish, tinged with roseate; valves gothic-arched, 

 the jugum subacute; entire surface minutely granulose ; lateral 

 areas conspicuously defined, having strong diagonal and sutural 

 ribs, provided with well projecting rounded grains; end valves hav- 

 ing subobsolete radiating riblets; central areas having about 8 dis- 

 tant, raised subgranulose longitudinal ribs on each side, the ribs 

 obsolete at the jugum ; interstices latticed with subradiating riblets ; 

 umbones conspicuous, the umbonal margin deeply toothed by a wart- 

 bearing rib, the teeth 8 to 10, obsolete toward the jugum ; margin 

 scarcely intorted. Umbo of posterior valve submedian, slightly pro- 

 jecting; margin elegantly pectinated. Interior: sinus large, flat, 

 sometimes serrate ; insertion-plates acute, broadly unifissate, end 

 valves having about 8 slits ; eaves conspicuous. Girdle having large 

 flat, striated scales. 



Length 61, breadth 2J mill.; divergence 90. (Cpr.) 



Catalina Island, 20-30 frns. 



Ischnochiton veredentiens CPR., Rep. Brit. Asso. Adv. Sci. 1863, 

 p. 649 ; Proc. Cal. Acad. Sci. iii, p. 211. 



A small arched species, sculptured like J. mertensii, but with two 

 rows of bosses, one of which dentates the sutures. The girdle scales 

 are rather large, flattened and striated, as in typical Ischnochiton. 



I. SERRATUS Carpenter. Un figured. 



Shell small, ashy, dotted here and there and especially at the 

 sutures with olive, sometimes spotted with red ; oval, subdepressed, 

 the sutures indistinct; entire surface most minutely granulated; 

 lateral areas strongly denned, provided with two to five very wide, 

 obtuse ribs, no interstices; posterior margins elegantly serrated. 

 Central areas having about 12 acute parallel ribs on each side; 

 jugum obtuse, scarcely umbonate ; with subradiating latticing ribs, 

 interstices impressed. Mucro median, obtuse. End valves having 

 about 20 obtuse ribs, like the lateral areas. Interior: median 

 valves bifissate, end valves with about 9 slits. Sutural plates large. 

 Girdle imbricated with large, scarcely striated scales. 



Length 82, breadth 5 mill. ; divergence 115. (O' r -) 



Cape St. Lucas, Lower California. 



Ischnochiton serratus CPR., Ann. & Mag. Nat. Hist. (3) xiii, p. 

 315, 1864. 



