Sliulips on marine Ostrarods 3n9 



some of tlieir distal liaii's were long (about the same as in iig. 6 of Ph. (Ph.) Lilljehorgi); the 

 most posterior-ventral bristles in this row are, however, sometimes almost completely smooth. 

 Inside the inner edge of the rostral incisur, somewhat posteriorly, there is a short, simple bristle. 

 Apart from tliese the rostrum and the part round the incisur are quite without bristles. A short 

 distance behind the incisur on a rather short part of the list there is a somewhat varying number 

 (about ten to twenty) of moderately long and finely feathered bristles; apart from these the list 

 is almost entirely without bristles along the ventral margin of the shell; inside the posterior 

 margin of the shell it has a moderate number of rather short, smooth, fine bristles. Along the 

 ventral margin of the shell the list is narrow, posteriorly it is somewhat wider. The selvage 

 is almost exactly similar in all the species of this genus that have been investigated by me. 

 It is well developed both on the rostrum and along the whole ventral side of the shell; on the 

 rostrum and along the edges of the incisur it is very wide (the incisur is quite filled by it), but 

 it is also rather wide along the whole ventral margin of the shell. On the rostrum and along 

 the edges of the incisur it is divided by a coarse striation into narrow rectangular portions; 

 this coarse striation gradually comes to an end, however, behind the incisur; along its whole 

 length the selvage is also finely cross-striated; this cross-striation is, however, sometimes rather 

 difficidt to verify with certainty at certain parts. On the rostrum the selvage has at the edge 

 rather fine hairs (cf. fig. 4 of Ph. (Ph.) Lilljehorgi) which vary in length; on the part along the 

 posterior edge of the incisur and just behind the incisur there are, in addition to such short hairs, 

 rather long marginal hairs as well, and, besides, issuing at about half the breadth of the selvage, 

 there are often a number of comparatively long bristles. Along the ventral margin of the shell 

 the selvage is also divided at the edge into short, fine hairs of different lengths; on the posterior 

 part they are somewhat shorter and more equal in length than they are anteriorly (see fig. 3 

 of Ph. (Ph.) Lilljeborgi). (In the specimens of Pli. ( Scleroconcha) Appellofi I have had an 

 opportunity of investigating the selvage was very nmch worn, so that all the details given here 

 — reproduced for Ph. (Ph.) Lilljeborgi — could not be verified with absolute certainty for them.) 

 Inside the list a part of the inner lamella of the shell just behind the rostral incisur is characterized 

 by about nine to twelve striae, situated close together and running parallel to the iuargin of the 

 shell (see fig. 2 of Ph. (Ph.) Lilljeborgi). With strong calcareous incrustati(jn. The forms 

 are rather large or of moderate size. 



Male: — This differs from that of the female especially by being considerably more 

 elongated and by having the rostral incisur considerably more shallow and wider. The two 

 sexes also seem to differ a good deal in length. The male shell is less strongly calcified. In those 

 cases in which a strongly marked sculpture is present it is less developed in this sex. 



First antenna: — This has strong sexual dimorphism. 



Female: — This is relatively short and has six joints. The original fifth joint is 

 not developed; whether, as G. W. MUller states, 1894, p. 23, the fourth joint has arisen by the 

 uniting of the original fourth and fifth joints seems to be very difficult to decide with certainty 

 at present; judging from the situation of the bristles the original fifth joint seems, at any rate 

 in this genus, to be very much reduced and it does not seem impossible tliat it has been eliminated, 

 at least in some forms, an assumption that seems to be supported by a comparison with the 



Zoolog. bidrapr, TJppsala. Siippl.-Eil. I. 47 



