PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 407 



The radala has a large flat, ovate central tooth with a thickened an- 

 terior edge but no marked cusp; on each side of this two rhomboidal 

 flat laterals with a similarly thickened anterior margin, the inner is the 

 larger and the outer sctmewhat more rounded in form; close to this are 

 two mhnite narroAv laterals with small cusps, hidden partly nnder the 

 cusps of the next or major lateral, for which reason they cannot well be 

 made out until the radula is i)artly torn apart or broken up; these two 

 little laterals are the most anterior of the transverse series, which has a 

 form like a very transverse M ; the major lateral has strong Docoglos- 

 sate features, being set on a flat plate whose posterior inner and anterior 

 outer corners are thickened and raised into the likeness of a pseudo- 

 cusp, the true shaft of the tooth being very short and terminating in a 

 strong tridentate pellucid cusp; the outer tooth is a squarish, plate-like 

 uncinus, exactly as in some chitons, with a thickened longitudinal ridge 

 near the inner margin. 



Length of shell about 10.0 ; width 7.5, and altitude 4.0'""'. 



Dredged by the United States Fish Commission in ISSl at stations 

 023, 940, and 050 in 00, 130, and 09 tathoms, sandy bottom, about 75 miles 

 S. and W. from Martha's Vineyard. Bottom temperature 52°, which 

 belongs ta the warmer bottom area. This very remarkable form would 

 have been called a " synthetic type" by Prof. Louis Agassiz. The shell 

 at once recalls Cajnilacnuva (= PiWlinm Midd,), which, however, is dis- 

 tinctively Tiienioglossate in dentition. The details of the branchial 

 leaves resemble those in Patella, the position of the branchiae and the 

 fotm of the head resemble Acmwa, the smooth thick mantle margin and 

 absence of eyes are characters found in Lepetidw. Some features in the 

 dentition recall Chitonirkc, and others CoccuUnidw. The position of the 

 animal in its shell is as in the Rhiphidoglossa universally. 



Nothing of the kind has been recognized in the collection made by 

 Messrs. Sigsbee and Bartlett, of the U. S. is^avy, in the Gulf of Mexico and 

 Antilles, nnder the supervision of Prof. Alex. Agassiz, on the United 

 States Coast Survey steamer Blake, leading to the supposition that this 

 may be a rather more northern form, though found in the warm area. 



Order DOCOGLOSSA. 

 Suborder ABRANCHIATA. 

 Animal destitute of external branchiae. Embryonic shell spiral. 

 Family LEPETID^ Gray. 



Lepetklw (Gray) Call. Ann. Mag. of Nat. Hist, vii, pp. 286-291, April. 



Subfamily LEPETIN^. 



Animal without eyes, without 1-ateral teeth, with a rhachidian tooth, 

 and erect uncini; muzzle with an entire margin, which is extended back- 



