PROCEEDINGS 



OK THE 



UNITED STATES NATIONAL MUSEUM. 



18 78. 



DESCRIPTIONS OF NEW FORmS OF mOI^LUSKS FRORI AI^ASKA 

 CONTAIIVED IIV THE COLLECTIONS OF THE NATIONAL 



racsEum, 

 By \¥. H. DALL. 



CHITONIDJE. 

 Genus AMICULA Gray. 



Type A, vestiia Sowerby. 



Subgenus Chlamydoohiton Dall. 

 Oh. t. ^Amiculce^ similiter set! branchiae ainbientes. 



Type Chiton amiculatus Pallas. 

 Amicula proper has the branchiae median. 



Genus LEPTOOHITON Gray. 



Leptochiton Belknapi Dall, u. s. 



L. t. elongate., valdeelevata,dorsualiter angulata; albidaplusminusve 

 cinereo et nigro tiucta; valvis elevatis, apicibus distinctis; mucrone 

 centrali conspicuo; sculptura ut in L. alveolo, sed granulis in areis dor- 

 sualis sparsim et quincuucialiter dispositis; valva postica sub apice con- 

 cava, postic^ sinuata; zona minima spiculis tenuibus versus marginem 

 munita. Lon. 10, lat. 3°"°. Div. 90o. 



fiat.— North Pacific Ocean, in lat. 53^ 08' N., and lon. 171° 19' W., 

 at a depth of 1006 fathoms, black sand and shells. Brought up in the 

 sounding-cup, on the sounding expedition of the United States ship 

 Tuscarora, Capt. George E. Belknap, U. S. N., in 1874. 



This specimen comes from a greater depth than any specimen of the 

 order hitherto collected. It is nearest toL. alveolus Sars, from the coast 

 of Norway. 



Genus TRACHYDERMON Cpr. 



Subgenus Trachyradsia Cpr. (Ms.). 



Trachydermou, valvis centralibus bi- seu pluii-flssatis. 



Type Chiton fulgetrnm Reeve. 

 Trachyradsia aleutica Dall, n. s. 



T. t.parva, rufo-ciuerea, oblonga, fornitata; jngo acutissimo; mucrone 

 Proc. Nat. Mus. 78 1 1 



