2 PEOCEEDIISrGS OF THE NATIONAL MUSEUM vol.72 



have hitherto been found only in antarctic regions. This species, 

 therefore, is of unusually great zoogeographicai interest, so I have 

 given in the following pages a detailed description of it as well as 

 a series of illustrations. 



The specimens of Brackerwidgia (XDvernarum Ulrich in the collec- 

 tion are in a very disjointed condition, and so I have refrained from 

 a close examination of them. From Ulrich's description and illus- 

 trations (Richardson, 1905, p. 700), it is very doubtful whether this 

 species belongs to the family Trichoniscidae (compare especially 

 Richardson, 1905, fig. 740^/). If it does, it occupies a very inde- 

 pendent position. I leave it to my American colleagues to answer 

 this question with the aid of fresh and better material. 



So far as can be judged at present, it is rather uncertain whether 

 North America possesses any terrestrial Isopods undoubtedly indige- 

 nous belonging to the family Trichoniscidae. 



As a result of these studies Trichoniscus papillicorms (Richard- 

 son) is made the type of a new genus DetoneUa; the supposed iden- 

 tity of Haplophthaknn^ puteus Hay with the earlier species H. dani- 

 cios Budde-Lund is confirmed, and a new variety of this latter, 

 H. danicus var. rotundatus^ is designated and briefly characterized. 



Family TRICHONISCIDAE Sars, 1899 



TRICHONISCUS PUSILLUS Brandt, 1833 



Localities. — Niagara Falls, N. Y. ; Haverford, Pa., H. Pratt, col- 

 lector. On fern leaf from England, intercepted at New York City, 

 January 22, 1924, Ivan Schiller, collector. 



Remarks. — Richardson, 1905 (p. 695), mentions no definite North 

 American localities for this species, but uses only the vague expres- 

 sion " North America." From the present collection no definite con- 

 clusion can be drawn. This species, which is very widespread, 

 especially in the north of Europe, may very probably be indigenous 

 at least in the eastern parts of North America. But it may also be 

 possible that, as with so many other terrestrial Isopods and Diplo- 

 pods, it was introduced from Europe and has since spread more or 

 less independently. It is for North American zoologists to try to 

 settle this question. 



The European " THchoniscus pusilhis " has proved to constitute 

 a collective species, containing a number of more or less nearly allied 

 species and subspecies that are to be definitely distinguished only by 

 means of the pleopods of the males. The greatest part of the 

 European " Trichoniscus pusillus,''^ however, comprises one species, 

 the true Trichoniscus pusillus Brandt. This is definitely settled 

 regarding western and northern Europe, and it is the most common 



