6 AV. M. TATTERSALL. 



other respects the ' Discovery ' material arid the ' Challenger ' types are in perfect 

 agreement, and the facts noted above establish the identity of the females here 

 referred to E. superba, with the species described by Sars as E. murrayi. It now remains 

 to show that the differences between E. murrayi and E. superba are only sexual. 



Male. Under the name E. superba Sars has described and figured this sex 

 adequately. The only point in which his description is deficient is the structure and 

 armature of the telson. He figures no dorsal spinules on the telson, and both describes 

 and figures the apex as slightly produced and obtusely pointed. Examination of Sars' 

 type shows that the apex of the telson is clearly broken, so that Sars' figure is in this 

 respect entirely imaginary. In the present material the apex of the telson is much 

 produced and acutely pointed, and the number of dorsal spinules is usually three pairs, 

 but may be four or two, placed as in Sars' figure of the telson of E. murrayi. One pair 

 of spinules still remains in Sars' type of E. superba, but the others had probably been 

 broken off (or obsolete ?). 



The most conspicuous difference between E. superba and E. murrayi, as described 

 by Sars, is the presence in the latter and absence in the former of a lateral denticle on 

 the carapace. But both Sars' E. murrayi were females, and his single specimen of 

 E. superba a male. In all the females in the present collection, the largest of which is 

 47 mm. in length, the spine on the lateral margin is large and prominent, and even in a 

 female, 50 mm. in length, in the collection from University College, Dundee, the spine 

 is equally well-developed. I have figured the spine of the latter specimen on PI. I., 

 Fig. 10. In male specimens, on the other hand, only those which are less than 42 mm. 

 in length have the spine well-developed (cf. PL I., Fig. 12, taken from a male, 39 mm. 

 in length). In males above 42 mm. up to 47 mm. in length the lateral spine on the 

 carapace is nearly obsolete and persists only as a blunt protuberance (cf. PI. I., 

 Fig. 11, taken from a specimen 45 mm. long, and also Coutiere (1906), PI. II., Fig. 22, 

 taken from a male of the same size). The ' Discovery ' collection contains no male 

 specimens exceeding 47 mm. in length, but the ' Challenger ' type measures 48 mm. 

 It is well preserved and shows no trace of the lateral spine at all. Obviously, then, the 

 absence of a spine is a sexual character confined to absolutely full-grown males only. 

 The remaining differences between E. superba and E. murrayi given by Sars are 

 as follows : 



(l) E. superba has the antennules considerably more robust than in E. murrayi 

 and the lobe from the second joint almost obsolete. This difference is, I think, a 

 purely sexual one, affording a parallel instance to that seen in the northern species, 

 Nyctiphanes couchi. PL L, Figs. 1 and 2 are taken respectively from male and 

 female specimens of the same size, viz., 45 mm., and from the same bottle. They 

 indicate, clearly, the difference in relative stoutness in the two sexes, and that of the 

 male shows the lobe from the second antennular joint in an intermediate stage of 

 reduction between that of the female and that shown by Sars in his figure of the male 

 E. superba, 48 mm. in length. 



