I9I9-1 



S. Kemp : Notes on Crustacea Decapoda. 



319 



former being exceedingly narrow ' ; the fifth segment is not chan- 

 nelled and the sixth is a little broader than long with straight, 

 slightly divergent sides. 



In the abdomen of the female the differences are less marked. 

 In S. invcstigatoris (text-fig. 56) it is rather broad, with slightly 

 convex sides and with the seventh segment narrow ; in S. proxi- 

 ma (text-fig. yc) it is proportionately narrower, with the sides a 

 trifle concave and the seventh segment broader. 



Among a large number of specimens of 5. proxima I have 

 found ten in which the abdomen does not correspond with the 

 normal type of either sex. In general outline (text-fig. yb) the 

 abdomen is similar to that of the normal male, but the constric- 

 tion at the junction of the fourth and fifth segments is less deep, 

 the fifth segment is proportionately broader and shorter and the 

 sixth broader with convex lateral margins. On raising the abdo- 

 men four pairs of pleopods are found as in normal females. 



Text-fig. 7. — Scophnera proxima, sp. nox- 



a. Abdomen of male. 



b. Abdomen of abnormal female. 



c. Abdomen of normal female. 



At first it seemed probable that these specimens were males, 

 infected by some parasite which had castrated them and rendered 

 abortive the normal development of the secondary male characters. 

 No parasite could, however, be discovered and on dissection 

 ovarian eggs were found which differed in no respect from those 

 obtained by the same method from normal females. There is, in 

 consequence, very little doubt that the specimens are females and 

 capable of breeding. 



That very aged females occasionally assume some of the 

 secondary sexual characters of the male is well known, but it does 

 not seem probable that this will aft'ord an explanation of the 

 abnormal females in 5, proxima. None of them is at all excep- 



i The sides of the constricted portion are bevelled, so that the seij^inents would 

 appear broader if viewed from beneath. 



