142 AMERICAN JOURNAL 



Soft parts. Body whitish, foot oval, thin, mantle entire, edge 

 thickened. Rostrum with two tentacular appendages ; anus 

 opening over the neck, also ? genital duct. No eyes ; tentacles 

 setaceous, short, thick ; no external gills. Rhachidian tooth 

 tricuspid ; central cusp long, pointed, black ; lateral cusps cen- 

 trally indented, giving the aspect of two denticles, on each side 

 of the central cusp. Shape rounded rhomboidal ; base delicately 

 impressed with longitudinal lines, thickened. Outer laterals 

 alated posteriorly, shafts pointed at the base. Inner laterals 

 similar, not alate ; cusps moderately broad, simple. Jaw simple, 

 edge entire, divided into two parts by an impressed median line. 

 Number examined, 20 specimens. 



A shell resembling this was described by Mliller in 1766, as 

 having the apex inclined posteriorly, and his statement has been 

 referred to this species, and copied by all subsequent authors. 

 On a careful inspection of many authentic specimens, some of 

 which still preserved the nuclear whorl, I am unable to find any 

 grounds for the statement. The apex is in almost every case 

 erect ; in a very few strongly inclined forward. In none does 

 it exhibit any tendency backward. It is true Miiller's specimen 

 may have been abnormal, but more probably he had in view a 

 specimen of Propilidium, in which the apex is reversed, but 

 which belongs to another family, although it has by Adams, 

 Gray, and others, since been confounded with our shell. Stimp- 

 son, and later, Jeffreys, very properly separated them, though, 

 pending the examination of the dentition, the precise position of 

 Proinlidium is doubtful. It has, however, distinct gills on the 

 back of the neck, which, as well as the apical septum, exclude it 

 from the Lepetidae. 



Loven's figure of the dentition of this species is ^orrect in 

 general effect, but incorrect in detail. This was doubtless due 

 to the imperfection of his microscope, or other similar circum- 

 stances. The figure represents the ribbon obtained from a dried 

 specimen from Norway, through Prof. Sars ; now in the Smith- 

 sonian collectiorh. 



Specimens from Norway, Finmark, Greenland, Nova Scotia 

 {L. Candida^ Couth.), Gaspe, and Grand Menan, have been ex- 

 amined, and no essential differences observed. 



Middendorff reports it from the Ochotsk, and Schrenck, copy- 

 ing him, from North Japan seas, but they probably refer to va- 

 rieties of the succeeding species, the shells having much general 

 resemblance ; though the anatomy of the animals shows them to 

 be generically distinct. 



Dr. Gray gives a copy of Miiller's original figure from the 

 Zool. Danica which shows no labial appendages, which strength- 



