PROCEEDINGS 



OF THE 



UNITED STATES NATIONAL MUSEUM. 



1 8 7 8. 



DESCRIPTIONS OF NEW FORMS OF MOLL1JSKS FROM ALASKA 



(<)\IA!M:i> in the collections of the national 



MUSEUM, 



By W. II. DALLi 



CHITONID.E. 



Genus AMICULA Gray. 



Type A. vestita Sowerby. 



Subgenus Chlamydochiton Dall. 



Ch. t. i Amiculce J similiter sed branchiae ambientes. 



Type Chiton amiculatus Pallas. 



Amicula proper has the branchiae median. 



Genus LEPTOCHITON Gray. 



Leptochiton Belknapi Dall, n. s. 



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

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

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

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

 cava, postice sinuata; zona minima spiculis tenuibus versus marginem 

 munita. Lou. 10, lat. 3 mm . Div. 90°. 



Eab.— North Pacific Ocean, in lat. 53° 08' N., and Ion. 171° 19' W., 

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

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

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



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

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

 of Norway. 



Genus TKACHYDERMON Cpr. 

 Subgenus Trachyradsia Cpr. (Ms.). 



Trachydermon, valvis centralibus bi- seu pluri-fissatis. 



Type Chiton fulgetrum Reeve. 

 Trachyradsia aleutica Dall, n. s. 

 T. t.parva, rufo-cinerea, oblonga, foroicataj jugo acutissimo; mucrone 

 Proc. Nat. Mus. 78 1 1 



