ISOPODS OF NORTH AMERICA. 429 



This species has three times been recorded from Greenland. 

 O. Fabricius recorded it as Oniscus ayuaticus. Kr0yer records it as 

 Asellus gronlandicus f He says of it: rt 



This species is without doubt the one mentioned by Fabricius under No. 227, and 

 which he himself did not see, although it does not appear to be rare. It approaches 

 so closely our Asellus rulgaris that it is extremely difficult to find sufficient distin- 

 guishing characters in the two. Nor am I entirely certain that I have found such 

 distinguishing characters, and therefore hesitatingly give this animal as a distinct 

 species, although it seems almost incredible to me that the fresh waters of both 

 Europe and Greenland should be inhabited by the identical species of Asellus. 



Hansen b says of Asellus granlandicus that it is probably not different 

 from Asellus aquations. 



Packard records it from Greenland as Asellus gronlandicus. 



Specimens collected in Greenland, sent to me from the Museum of 

 Comparative Zoology at Harvard University and labeled Asellus 

 gronlandicus^ do not differ in any respect from Asellus aquaticus as 

 described and figured by G. O. Sars. 



Body narrow, elongate, nearly three times as long as wide, 3 mm: 

 8 mm., narrower anteriorly and becoming wider posteriori}". 3 mm. 

 is its greatest breadth. 



Head about twice as wide as long, 1 mm: 2 mm., with the anterior 

 margin slightly excavate. Lateral margins entire, with a small lobe 

 on either side near the posterior margin. Eyes small, distinct, com- 

 posed of only three or four ocelli and situated close to the lateral 

 margin, halfway between the anterior and posterior margins. The 

 first pair of antennae have the basal article large and dilated ; the second 

 article is half as wide and but little longer; the third article is two- 

 thirds the length of the second. The flagellum is composed of eleven 

 articles and extends to the end of the peduncle of the second pair of 

 antennas. The second pair of antennas have the first two articles short 

 and subequal; the third is one and a half times longer than the second; 

 the fourth article is nearly as long as the first three taken together; 

 the fifth is one and two-thirds times as long as the fourth. The flagel- 

 lum is composed of about forty-four articles, and extends to the pos- 

 terior margin of the fifth thoracic segment. It measures 6 mm. in 

 length. 



The first segment of the thorax has the epimera conspicuous and 

 situated in the antero-lateral corners. In the second and third seg- 

 ments they are small and almost inconspicuous lobes situated at the 

 antero-lateral corners of the segments. In the fourth segment they 

 are small and inconspicuous and situated just below the antero-lateral 



o Kongelige danske videnskabernes Selskabs naturvidenskabelige og mathematiske 

 Afhandlinger, VII, 1838, p. 318. 



& Videnskabelige Meddelelser fra den naturhistoriske Forening i Kj0benhavn, 

 1887-88, p. 190. 



