216 M. C. Mereschkowsky on sojne 



the length of which is two or three times its greatest breadth. 

 The carapace is borne upon a peduncle three times its length, 

 of a cylindrical form, thin, and of equal thickness throughout. 

 This peduncle is inserted into the carapace without causing 

 any constriction at the point of union, as is the case, for 

 example, in Acineta patula ; it is straight in the normal state*, 

 and hollow, the cavity of the peduncle being continued insen- 

 sibly into that of the conical carapace without interruption. 

 Close to the margin of the aperture of the carapace the walls 

 of the latter are recurved suddenly inwards, and thus form a 

 second carapace, situated in the interior of the first, and only 

 united with the latter at the margin of the aperture. The 

 second, or interior carapace occupies more than one third of the 

 outer carapace, sometimes even one half of it, and is charac- 

 terized by its rounded bottom and slightly turned-out margins. 

 What further characterizes this species is a system of trans- 

 verse circular strige covering the whole surface of the exterior 

 conical carapace ; but as these stria3 are extremely fine, they 

 are only visible when a high magnifying-power is employed. 



I have only seen the elongated oval body of Acineta Sa'i- 

 fulce adhering to the margins of the carapace and freely sus- 

 pended in the second carapace ; but, as I have only observed 

 this species when preserved in alcohol, it may be that the 

 body of the living animal adheres to the whole surface of the 

 inner carapace, which would thus perhaps not be easy to 

 observe. A part of the body, in the form of a regular hemi- 

 sphere, issues from the aperture of the carapace ; and the 

 whole of this part bears suckers (shortened by the action of 

 alcohol), arranged regularly over the spherical surface. The 

 small oval nucleus is situated in the middle, but nearer to the 

 free half of the body. The protoplasm is, as usual, filled with 

 fatty granules, and presents a slight yellowish coloration ; the 

 carapace and the peduncle are absolutely colourless. 



The following measurements of this species have all been 

 taken from individuals preserved in alcohol : — 



millim. 



Length of the carapace 0'063 



Maximum breadth 0-027 



Length of the whole animal, including the 



peduncle 0-135 



Breadth of the peduncle 0-0021 



Log. White Sea: — 1. Bay of Onega, near the town of 

 Rem, at a depth of 5 fathoms, on a muddy bottom, on the 



* The figure represents a curved peduncle ; but this form is due to 

 artificial compression, rendered permanent by the action of alcohol. 



