DESCRIPTION OF A NEW ISOPOD OF THE GENUS NOTA- 

 SELLUS FROM THE EAST COAST OF PATAGONIA. 



By Harriet Richardson, 



Collaborator, Division of Marine Invertebrates, U. S. National Museum. 



Two specimens of a new species of Notasellus were collected by the 

 U. S. Bureau of Fisheries steamer Albatross in 1888 off the east coast 

 of Patagonia. The first species of this genus, N. sarsii, from South 

 Georgia, was described by Pfeffer" in 1886. In 1902, Dr. T. V. Hodg- 

 son 6 described a second species, N. australis, from off Cape Adare. 

 In 1905, Stebbing c referred Stenetrium inerme Haswell to the genus 

 Notasellus. 



NOTASELLUS TRILOBATUS, new species. 



Body narrow, elongate ; surface smooth. Color, in alcohol, yellow. 

 Head wider than long, with the antero-lateral angles rounded, and 

 the front produced in the middle in a long rostrum, rounded at the 

 extremity. The rostrum extends to the end of the third article of 

 the second pair of antenna?. The eyes are rather large, composite, 

 and placed in the post-lateral angles of the head. The first antenna? 

 have the first article of the peduncle dilated; the second article 

 is narrower and shorter; the third is shorter than the second; the 

 flagellum is short, is composed of eleven articles, and extends a 

 little beyond the middle of the fifth article of the peduncle of the 

 second antenna?. The second antenna? have the first four articles 

 short; a scale is articulated to the third article; the fourth article is 

 about one and a half times as long as the first four articles taken 

 together; the sixth article is about one and a half times longer than 

 the fifth; the flagellum is multi-articulate. The first segment of the 

 thorax has the post-lateral angles acutely produced, the antero- 

 lateral angles rounded, and the epimeron, which is bilobate, situated 

 on the lateral margin anterior to the post-lateral angles. The three 

 following segments have both the antero-lateral and post-lateral angles 

 produced in a process, with the margin between them straight and 

 occupied by the bilobate epimeron. The last three segments have 

 only the antero-lateral angles produced, the post-lateral angles being 

 rounded and occupied by the single-lobed epimeron. 



a Jahrb. Hamburgischen Wiss. Anst., vol. 3, 1886, pp. 125-134, pi. 7, figs. 5-28. 

 b Crust. Southern Cross Coll., 1902, pp. 251-253, pi. 36. 

 c Ceylon Pearl Oyster Fisheries, pt. 4, p. 55. 



Proceedings U. S. National Museum, Vol. 37— No. 1720. 



649 



