Deep-water Limpets and Chitons. . 19 
this two rhomboidal flat laterals with a similarly thickened 
anterior margin; the inner is the larger, and the outer some- 
what more rounded in form; close to this are two minute 
narrow laterals with small cusps, hidden partly under the cusps 
of the next or major lateral, for which reason they cannot well 
be made out until the radula is partly 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 Docoglossate features, being set on a flat 
plate whose posterior inner and anterior outer corners are 
thickened and raised into the likeness of a pseudocusp, 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 someChitons, with a thickened 
longitudinal ridge near the inner margin. 
Length of shell about 10:0, width 7:5, and altitude 4:0 
millim. 
Dredged by the United-States Fish Commission in 1881 
at stations 923, 940, and 950, in 96, 130, and 69 fathoms, 
sandy bottom, about 75 miles 8. and W. from Martha’s Vine- 
yard. Bottom-temperature 52°, which belongs to the warmer 
bottom area. This very remarkable form would have been 
called a “synthetic type” by Prof. Louis Agassiz. The 
shell at once recalls Capulacmea (= Pilidium, Midd.), which, 
however, is distinctively Teenioglossate in dentition. The 
details of the branchial leavesresemble those in Patella, the posi- 
tion of the branchiz and the form of the head resemble Acmea, 
the smooth, thick, mantle-margin and absence of eyes are 
characters found in Lepetide. Some features in the dentition 
recall Chitonide, and others Cocculinide. 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. Navy, in 
the Gulf of Mexico and Antilles, under 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 branchiz. Embryonic shell 
spiral. 
Family Lepetide, Gray. 
Lepetide (Gray), Dall, Ann. & Mag. Nat. Hist. 1871, vii. pp. 286-291. 
Q% 
