158 Transactions. — Zoology. 



finger, each row containing about twelve spines. On the outside there is a 

 central row, and also several other spines more or less irregularly placed. 

 On the outer edge the dactylopodite bears two rows of spines, six in one 

 and four in the other, and there are two small spines at the tip. Each 

 finger ends in a strong spine pointing towards each other, and on the inside 

 of the fingers are three or four rounded prominences. There are numerous 

 tufts of setae on most of the joints, but most abundantly on the propodite. 



The four posterior pairs of ambulatory legs are somewhat sleuder ; in all 

 except the last the coxopodite bears a podobranchia and a small tuft of 

 coxopoditic setae. 



The first pair of abdominal appendages are entirely absent both in the 

 male and female. 



The second, third, fourth and fifth abdominal appendages are all alike, and 

 are rather simpler than those of Astacus. The coxopodite (pi. XX., fig. 1 

 cxp) is very short, and is followed by the long cylindrical basipodite (bp) 

 which supports the exopodite (e.v) and the endopodite (en). In the male 

 these are of about equal length, and are imperfectly articulated through 

 their whole length, neither of them having an undivided basal joint as in 

 Astacus. Their edges are fringed with long plumose setae. In a female 

 with the eggs attached under the abdomen the appendages (pi. XX., fig. 2) 

 were found to differ somewhat from those of the male. They were much 

 slenderer and the exoskeleton was much softer ; the endopodite (en) was 

 considerably longer than the exopodite (ex), and in both the articulations 

 were very indistinct ; the setae were long and did not appear to be plumose. 

 In a young female, however, in which the eggs were still in the ovary, the 

 abdominal appendages were much more like those of the male, and were 

 supplied with plumose setae. 



The appendages of the sixth abdominal somite have the coxopodite (pi. 

 XX., fig. 3, cxp) broad and indistinctly divided into two or three parts. The 

 exopodite (ex) is in the form of a broad oval plate divided into two parts by 

 a transverse hinge, the basal part ends distally in a row of short spines of 

 which the outside one is the longest. The terminal portion is rounded and 

 fringed with plumose setaa. A median ridge runs from the coxopodite 

 through the whole length of the exopodite. The endopodite (en) is of 

 similar shape, but consists of one piece only, the median ridge ends in a 

 sharp spine at some distance from the edge. 



Respiratory organs. — These differ considerably from those of Astacus, 

 and closely resemble those of Astacopsis.* The epipodite of the first maxil- 

 lipede is in the form of a broad more or less oval-shaped lamina, the end of 

 which bears numerous branchial filaments similar to the filaments of the 



* "The Crayfish," p. 264. 



