410 PROCEEDINGS OF UXITED STATES NATIONAL MUSEUM. 



ture externally of fine, uniform, rounded, closely-set threads, radiating 

 from near the apex to the margin, and reticulated by the fine, rather 

 prominent, regular, concentric ridges of growth, both ridges and threads 

 averaging near the margin about three and a half to the millimeter. 

 Lon. from end to end, 14.5"""; from apex to anterior end, 5.5"^^ -, lat. 

 10.0'"""; alt. 5.5""\ 



Habitat. — West Indies ; St. Thomas, in coral ; Santa Lucia, station 

 215, in 226 fathoms, Blake expedition. 



The examination of a well preserved specimen showed that the end 

 of the muzzle formed a semilunar area with a distinctly-marked margin 

 and lappets at the posterior corners. In tlie middle of this flat and 

 nearly smooth area is the mouth, surrounded by a small circular papillose 

 area. The jaw is thin and translucent, but sufficiently strong to resist 

 contraction on the drying up of the soft parts. The radula contains 

 about 175 series of teeth, which are large, with strong cusps, which are 

 turned toward the middle line of the radula and strongly denticulate. 

 The denticulate part, as in most Bocoglossa, is nearly black, the anterior 

 denticles are larger, the posterior nine subequal in size, the whole num- 

 ber of denticles is twelve; the whole tooth has somewhat the appear- 

 ance of a coarse curry-comb, and suggests that it is due to a con- 

 solidation of the normal three Docoglossal laterals rather than the 

 suppression of all but one and the modification of that one. 



The protrusion of the anterior arch of the head is very peculiar and 

 remarkable; the foot is rather short for the size of the shell; otherwise 

 the features are those of Acmwa, in general. The gill is rather large 

 and exactly as in Acma^a. ® 



The number of teeth is the smallest known in any limpet, and none 

 of the same shape have been recorded in the order. It is likely, how- 

 ever, that Scutellina, w^hen investigated, will prove to have very similar 

 dentition.* 



CHITOXID^. 



Genus Ch^topleuea (Shuttleworth) Cpr. 



Cha^topleura apicuJata Say. 



Habitat. — Station 938, United States Fish Commission, 1881, being 

 100 miles SB. by E. ^ E. (magnetic) irom Gay Head Light, Martha's 

 Vineyard. The depth was 210 fathoms, green sand and mud, the bottom 

 temperature lO^.S, the surface 72°.0 F. 



In these researches only two specimens of Chitonidw were obtained, 

 and these are not of a genus characteristic of the deeps. These speci- 

 men were young, but did not differ from young ones of the same species 

 from shallow water. There have been fodnd in depths of 100 fathoms 



* I should be most thankful for a dried or alcoholic specimen of the soft parts of the 

 tjTiieal species of Scutellitia {S. crenulata Broderip). 



