REPORT ON THE SCHIZOPODA. 15 



To show the correctness of this assumption, and at the same time afford other 

 zoologists an opportunity of instituting a comparison, I have given on the first Plate 

 of the present Report figures of the Challenger specimens, and subjoin the following 

 descriptive notes. 



The male specimen (fig. 1) has a length of 25 mm., and is distinguished from 

 the female (fig. 2) by a somewhat more powerful development of the tail, as also by 

 the greater length of the outer antennular flagellum. 



The broad frontal plate, which is hollowed in the centre (fig. 3), has the median tooth 

 (rostrum) rather short, not exceeding in length the lateral teeth (supra-orbital spines), 

 and covers, as in the Norwegian form, not only a great pail of the antennular jieduncles, 

 but also the bases of the globular eyes, forming here a kind of imperfect orbit. 



The antennal scale (fig. 3) exhibits the peculiar cordiform shape characteristic of the 

 species, but in the present specimen is distinguished by the unusually small numljer of 

 teeth (only three) on the outer margin. 



Having examined a series of Norwegian specimens, I find, however, that the number 

 of teeth along the outer edge of the antennal scale, as well as the relative length of the 

 teeth on the frontal plate, is subject to a rather considerable variation. This, too, is 

 obvious on comparing the male specimen here described with the two other specimens 

 procured from the Challenger Expedition, which are both females. 



One of these females, the most perfect, is represented in fig. 2, viewed from above. 

 It has a length of 18 mm., and thus is somewhat smaller than the male specimen, a 

 fact in accordance with that observed in the Norwegian forms, the females of which 

 are, as a rule, considerably smaller than the adult males. 



It wiU be observed, that the median tooth of the frontal plate in this specimen is 

 rather more produced than the lateral teeth, reaching almost to the end of the antennular 

 peduncle. Moreover, the number of teeth along the outer edge of the antennal scale 

 (fig. 4) is greater, as many as five having been counted. 



Of the legs, I have figured one belonging to the last pair (fig. 5) in the imperfect 

 female specimen. On comparing this figure ^\ath the one given by my father of 

 the same leg in a Norwegian specimen^ the resemblance between the two is very 

 striking. 



The caudal fan (fig. 6) also exhibits in all its details the most perfect agreement 

 with that of the Norwegian form. The telson, considerably exceeding in length the 

 uropoda, is scooped out dorsally along the middle, exhibiting two parallel longitudinal 

 carinse, most prominent in the posterior part. It tapers gradually towards the apex, 

 and, a little posterior to the middle, is provided on either side with tluree small lateral 

 denticles. To the truncate extremity of the telson are attached four strong spines, and 

 a little anterior to them is observed another somewhat smaller spine on either side. In 



1 See Univ. Progr., pi. ii. fig. 36. 



