ISOPODS OF NORTH AMERICA. 



57 



Description of male. This species is closely related to Gnathia 

 hirsuta (Sars), but differs from all other species of the genus in the 

 structure of the mandibles. 



The body is very short; the thorax is a little narrower than long in 

 the median line. The fourth free segment of the thorax (fifth seg- 

 ment) is scarcely longer than the fifth segment. The fifth free seg- 

 ment (sixth segment) has large lateral areas, 

 posteriorly very much elongated, with the 

 posterior angles subrotund. 



The abdomen in the specimen is almost 

 entirely wanting. 



The head and the first two free segments 

 of the body are very rough and ornamented 

 with acute processes and numerous tuber- 

 cles; the third free segment (fourth seg- 

 ment) is ornamented with smaller tubercles 

 at the anterior portion, but is smooth poste- 

 riorly; the fourth free segment (fifth seg- 

 ment) has large swollen lateral areas, orna- 

 mented with a few tubercles, the median 

 part being smooth; the fifth free segment 

 (sixth segment) is smooth. The eyes are 

 rather large, manifest. The mandibles are 

 large, ornamented on the basal half of the superior margin with a very 

 high crest irregularly notched or dentated. The teeth of the crest 

 have the apex rounded. 



The legs are long, rather robust, furnished with many processes, for 

 the most part, large. The body and the legs are furnished with a few 

 hairs. Length of the head and thorax together 3.1 mm. 



Only a single mutilated specimen/' 



The above description is adapted from the following description of Hansen's: 

 Specimen singulum masculinum sat mutilatujn vidi. Anceo hirsute G. O. Sars 

 sat affinis, structura mandibularum a speciebus omnibus mihi cognitis diversus. 

 Corpus brevius; truncus paulo augustior quam in linea media longior. Segmentum 

 quartum liberum trunci segmento quinto vix longius; segmentum quintum areis 

 lateralibus magnis, post valde elongatis, angulis posterioribus subrotundatis. (Cauda 

 in specimine fere tota deest. ) Caput et segmenta duo anteriora libera trunci scabra, 

 processulis acutis et tuberculis permultis ornata; segmentum tertium liberum ante 

 tuberculis minoribus instructum, postice glabrum; segmentum quartum area laterali 

 magna, inflata, tuberculis nonnullis decorata, parte media glabra; segmentum quin- 

 tum glabrum. Oculi sat magni, dilutiores. Mandibulse rnagnse, parte dimidia basali 

 marginis superioris crista valde elevata et irregulariter inciso-dentata ornata; dentes 

 cristee apice rotundato. Pedes longi, sat robusti, processulis multis, ex parte magnis, 

 muniti. Corpus pedesque setis nonnullis instructa. Long, capitis et trunci juncti 3, 

 1 mm. HANSEN, Vidensk. Meddel. Naturh. Foren. i Kj0bh., 1887-88, p. 182. 



FIG. 41. GNATHIA CKISTATA 

 (AFTER HANSEN). a, RIGHT MAN- 

 DIBLE (INNER SIDE), b, MALE 



(SOMEWHAT MUTILATED) (EN- 

 LARGED.) 



? 



LIBRARY. 



