No. 1633. SOME NEW ATLANTIC ISOPOD A— RICHARDSON. 77 



This species differs from the species described by Sars, Haplonis- 

 cus bicuspis, in having the front of the head excavate, in having the 

 flagellum of the second antenna 1 composed of eight articles instead of 

 thirteen, and in the broader abdomen in proportion to its length with 

 the larger and differently shaped median lobe. 



HAPLONISCUS RETROSPINIS, new species. 



This species is more similar to Haploniscus bicuspis (Sars) in the 

 shape of the head, which does not have the front excavated as in the 

 preceding species. It differs, however, from Sars's species in having 

 the flagellum of the antennae composed of ten articles instead of 

 thirteen and in having the post -lateral teeth of the abdomen longer; 

 the teeth are twice as long as the uropoda in the female and about 

 four times as long in the male, while in Sars's species they do not 

 exceed the length of the uropoda. 



About seventeen specimens, two males and fifteen females, were 

 collected at Station 2547, south of Marthas Vineyard: they were 

 taken at a depth of 390 fathoms. 



The type is in the U. 8. National Museum. Cat. No. 38966. 

 Genus JANIRELLA Bonnier, 1896. 



Head with a prominent rostrum : lateral margins of head and of 

 all the segments of the body produced in prominent processes. Eyes 

 absent. First pair of antenna 1 with the peduncle composed of three 

 articles; flagellum composed of several articles. Second pair of 

 antennae with the third article of the peduncle furnished with an an- 

 tennal scale. 



Terminal segment of body triangularly produced at the apex; uro- 

 poda biarticulate, consisting of two small articles. 



Legs all ambulatory. 



The second antennae of this and the preceding genus, as in the 

 genus Nannoniscus Sars, resemble the Janh'Uhv in having the pedun- 

 cle composed of six articles, the third furnished with an antennal 

 scale; they also with Nannoniscus, in the total absence of eyes, and in 

 the character of the uropods (which are biarticulate and composed of 

 two subequal articles in the present genus, but unarticulate in the 

 preceding genus) resemble the Desmosomidae ; but, as Sars says of 

 Nannoniscus, in the general form of the body, in the structure of the 

 legs and antennae they resemble the Janiridae. 



This genus differs from Nannoniscus in lacking the olfactory 

 papilla to the first antenna, in having the peduncle of the first antenna 

 composed of three articles, in having all the lateral margins of the 

 body produced in processes, in the shape of the terminal segment of 

 the body, and in having the uropoda composed of two articles, 

 biarticulate and not double-branched as in that genus. 



The type of the genus is Janirella nuns, ni Bonnier. 



a Ann. Univ. Lyon, 1S9G, pp. 587-593. 



