studies on marine Oslratods 371 



them four to six proximal and four distal sensorial filaments were observed, on the posterior 

 one three to six proximal ones and four distal ones. 



Male: — This is somewhat more elongated than that of the female; as an instance it 

 may be mentioned that some males of Ph. (Pli.) glohosa with shells about 3 mm. long had first 

 antennae about 1,8 — 1,9 mm. long, while on some females of the same species with about the 

 same length of shell as the above-mentioned males this limb was only about 1,4 — l,(i mm. It has 

 six joints. The original fifth joint is represented by a small, reduced part, most strongh- 

 developed posteriorly (where the sensory bristle of the fifth joint is attaclied); it is in most 

 cases rather clearly defined from the fom-th Joint (cf. the accompanying figure 8 of Pli. (Ph.) 

 (jlobosa), but it might perhaps, all the same, be convenient to foUow Cx. W. MClleh and not 

 to take this part as a special joint. The original eighth joint is somewhat displaced laterally; 

 traces of a union between this joint and the original seventh joint can still be observed. The 

 proportions between the joints seem to be fairly constant and about as follows; (the figures 

 are taken from measurements of Pli. (Ph.) glohosa: 



V'- II ""• III ' • IV '' • V ' • VI " 

 The comparatively strong development of the end joint seems to be specially noticeable. 

 Bristles: In this sex, contrary to the female, there is found on the part that has been stated 

 above to be the remains of the original fifth joint a very well-developed posterior sensory bristle. This 

 sensory bristle seems to be developed in about the same way in all the species of this genus; 

 it is about as long as the anterior side of the second joint, is rather thick and is strongly annulated 

 proximally, grows very narrow distally and is very finely annulated there or quite hyaline; 

 on its posterior side it has, along the proximal half, very numerous thin bare, distally rounded 

 sensorial filaments, of about a uniform thickness throughout and ending with a short, fine hair; 

 in most cases these filaments are somewhat more than half the length of the bristle; on the 

 distal half this bristle has only a few sensorial filaments of the same t^-pe as the proximal ones, 

 but considerably shorter. With the exception of this bristle the second to the fifth (definitive) 

 j(jints have the same bristles as these joints on the female first antenna and these bristles show 

 in most cases about the same type in both sexes. The end joint has the same number of bristles 

 as in the sub-family CyprkUninae, i. e. seven, three of which are, as in this sub-family, attached 

 to the original seventh joint, four to the original eighth joint; only one posterior bristle is devel- 

 oped in this sex on the original seventh joint. With regard to their types they show rather close 

 agreement with the corresponding bristles in the female; in length they are, however, very dissi- 

 milar, as the anterior and medial bristles of the original seventh joint and the two lateral and the 

 posterior medial bristles on the original eighth joint are rather considerably shortened, while 

 the posterior bristle of the original seventh joint and the anterior- medial bristle of the original 

 eighth joint are very much lengthened; the two latter bristles are about as long as the shell. The 

 number of sensorial filaments on the bristles of the end joint is often different in the two sexes. 



Second antenna: — This shows strong sexual dinu)rphism. 



Female: — The p r o t o p o d i t e has no bristles. The e x o p o d i t e is somewhat 

 longer than the protopodite (exopodite : protopodite aliout fO— 7] : a). Tlie proportion between 

 the joints is about the same in all species: 



