ISCHNOCHITON. i 



Trachydermon gothicus CARPENTER, Kep. Brit. Asso. Adv. Sci. 

 1863, p. 649 ; Proc. Cal. Acad. Sci. iii, p. 212, 1866 ; MS. p. 18. 



An unusual character in this very 'small, prettily sculptured spe- 

 cies is that the sutural laminae are slightly connected [across the 

 jugal sinus] by a layer lining the very broad, shallow sinus. As in 

 pseudodentiens \_=dentiem Gld.] a false appearance of dentation is 

 given to the sutures by the spots of darker painting. (Cpr., MS.) 



ISCHNOCHITON. 



I. RETIPOROSUS Carpenter. Unfigured. 



Shell small, subelongate, a % shen colored ; much elevated, the jugum 

 arcuate. Valves subquadrate, apices concealed, lateral areas little 

 defined, having 3 to 6 rounded, obsolete riblets, here and there with 

 acute projecting granules. Central areas pitted all over, interstices 

 small, punctate. Terminal valves with more acute close narrow 

 riblets. Mucro little raised, anterior. Inside with broad sutural 

 sinus. Insertion plates of intermediate valves with one slit on each 

 side, terminal valves with about 12 slits. Girdle bearing close, 

 minute scales, which are little elongated. 



Length 11, breadth 7 mill.; div. 90. 



Puget Sound- 



Trachydermon retiporosus CPR., Brit. Asso. Rep. 1863, p. 649. 

 Ischnochiton (Trachydermon) retiporosus CPR., Proc. Acad. -Nat. 

 Sci. Phila. 1865, p. 59. 



A species like scrobiculatus Midd., the central pattern in net- 

 work, lateral areas with 3 to 6 ribs. 



Known to me only by Carpenter's description. 



I. FLECTENS Carpenter. Unfigured. 



Shell small, subelongate, roseate; jugum acute; lateral areas 

 scarcely defined. Valve margins excurved, suture incurved, apices 

 very prominent ; valves having minute, not very close granules 

 sparsely subradiating, all over very minutely punctulate. Mucro 

 conspicuous, anterior. Inside : sutural sinus wide, flat ; eaves 

 scarcely projecting. Terminal valves with 11, median 1 slit. 

 Girdle very minutely granulate. 



Length 8f, breadth 6 mill. ; div. 110. (Cpr.) 



Puget Sound. 



