Stiiilios on inariiio Oslracoils 457 



the number difiering in different species. Separated from these bristles by a marked gap there 

 is along the posterior part of the ventral margin a smaller or larger number of bristles, the anterior 

 ones of which are usually rather short, the posterior ones moderately long. All these ventral 

 bristles have rather long and often rather fine hairs along a smaller or greater part of their length 

 and have short hairs distally; the posterior ones, however, often have long hairs right to their 

 points. Some of the bristles along the anterior edge of the anterior sole-shaped flattened part 

 of the ventral side always seem to be developed, the other ventral bristles may be quite absent; 

 cf. A. aherrata. This limb is covered to a great extent with abundant short, fine hairs, many 

 of which are arranged in groups. 



Seventh limb: — 



Female: — This is moderately long; in one female specimen of ^. norvegica the 

 shell of which was 2,1 mm. long it was 1,2 mm. The distal part of the limb is rather slightly 

 widened and is supported by rather broad chitinous rings, which articulate with each other 

 at the middle by processes, both on the medial and the lateral side. The rings situated more 

 proximally on the limb have no such processes and are also narrower and often rather 

 irregular. Near the point of the limb there is an oval of irregular chitinous pieces, moveably 

 joined to one another and enclosing a longitudinal muscle consisting of four parts; this apparatus 

 is apparently used to press the end combs against each other; cf. A. Grimaldi var. vicina, fig. 2; 

 this apparatus is, however, often rather difficult to observe with certainty. There are a com- 

 paratively small number of cleaning bristles, never more than one on the same side of the same 

 ring. Their number and position vary to some extent, but not so much that they cannot be 

 used as characteristics of the species. Each cleaning bristle has a rather small number (from 

 one to five were observed) of bells, cut off transversally; the tongue of its terminal bell is cut 

 off rather obliquely. Proximally of the bells the cleaning bristles are bare. There are only 

 two symmetrical end combs with teeth of a somewhat varying type; these teeth are character- 

 ized by the fact that they are always fm-nished with a larger or smaller number of fine or more 

 or less coarse secondary teeth arranged in the shape of a feather. 



Male: — This has sometimes rather fewer bells on the cleaning bristles. 



F u r c a: — This has very slight or is sometimes even quite without sexual dimorphism. 



Female: — The lamellae are short, their breadth is somewhat greater than their 

 length. Each lamella is armed with from seven to ten claws, all well divided from the lamella. 

 The anterior claw is comparatively long, the others decrease fairly uniformly in length posteriorly, 

 the posterior ones are short and are shaped like bristles. A division into main claws and second- 

 ary claws is, at least in many cases, almost conditional; at least the five anterior ones must, 

 however, be considered as main claws. The claws are rather weakly curved along the greater 

 part of their length; distally, on the other hand, they are rather strongly curved. The posterior 

 bristle-like claws are often rather strongly and irregularly curved; the tj'pe is shown in fig. 17, 

 A. Grimaldi. Only one out of all the species investigated by me was characterized by another 

 type of claws; cf. fig. 12, A. aherrata. The main claws are armed ventrally with two rows, one 

 medial and one lateral, of short, strong, pointed teeth. In all the species of this genus described 

 in this treatise a number of these teeth are of somewhat greater length; on each claw from 



Zootoy. bidmn, Uppsiitii. Suppl-Kil. I. ^" 



