PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 319 



Leptochiton nexus. 



L. nexus Opr. Suppl. Rep. Br. As. 1833, p. 650. 

 Sab. — California, Cooper. 



Leptochiton internexus and var. rugatus. 

 L. internexus Cpr. MSS. 



Hab. — California, Cooper, Canfield and Hemphill. 



Hanleyia mendicaria. 



Chiton mendicarius Mighels & Adams, Boston Journ. N. H. iv, p. 42, pi. iv, 

 f. 8, 1842. 



Hanleyia mendicaria Cpr. N. Engl. Chitons, 1. c. p. 154, 1873. 



Hab. — Casco Bay; Grand Manan, Stiinpson; Portland Harbor, Me., 

 TJ. S. Fish Commission. Deep-water specimens much larger than those 

 from shallow water. 



Hanleyia debilis. 



Hanleyia debilis Gray, Guide, p. 183, 1857. 



Chiton Hanleyi Bean, Brit. Mar. Conch, p. 232, f. 57, 1844. — Sars, 1. c. p. 109, 

 pi. 7, f. 5 a-i, 1878. 



Hab. — British seas northward; Mageroe near North Cape, 25-300 f., 

 Sars. Stellwagen Bank, Mass. Bay, 38 fathoms, gravel; TJ. S. Fish 

 Com., 1878. Type of the subgenus. A recent addition to our North- 

 east American fauna. 



Hanleyia (?) abyssorum. 



Chiton abyssorum M. Sars, MSS.— G. O. Sars, 1. c. p. 109, pi. 7, f. 4 a-c, pL I, 

 f. 6 a-c, 1878. 



Hab. — Bergen, Norway, 150-200 fathoms, Sars, L c. 



The teeth of this species as figured by Sars agree pretty well with 

 those of H. mendicaria, but neither Prof. Sars' figures nor his descrip- 

 tion afford means for determining its generic position. The valves of 

 the two specimens figured exhibit rather remarkable differences, and, 

 this variation admitted, the question arises, Is this more than a gigantic 

 form of the preceding ? 



Hanleyia tropicalis. 



A large and beautiful species from the deep waters of the Gulf of 

 Mexico is the only other recognized species of the genus, and Avill be 

 described by the writer in the Beport on the Deep-sea Dredgings made 

 under the supervision of Prof. A. Agassiz, on the U. S. Coast Survey 

 steamer Blake, in 1878. 



ISCHNOIDEA. 



Genus TRACHYDERMON Cpr. 



Tracliydcrmon Cpr. Suppl. Rop. Br. As. 18G3, p. C49, as a subgenus of hchnochx ton, typo 



Chiton cinereus Lowe. 

 Lcpidoplcurus sp. auct. 

 > Craspedochilm G. O. Sars, 1. c. p. 114. 



