22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



MICROSPIROBOLUS DORSETTI, n. sp. 



Two males and two females were collected near Roadtown, Tor- 

 tola Island, by P. H. Dorsett, March i8, 1932. 



Diagnosis. — This species may be rather closely related to M. rich- 

 mondi Chamberlin, as shown by the gonopods, but its principal differ- 

 ences are the larger size, greater number of segments, different col- 

 oration, and the lack of an impressed sulcus across any of the seg- 

 ments except a few near the head. 



Description. — Length of the largest specimen, a female, 32 mm, 

 width 2.y mm. Number of segments 46 to 50. 



Living colors : Head solid black ; first segment salmon in front, 

 changing to cream behind, the posterior margin narrowly black. Seg- 

 ments 2 to 6 dark throughout. Ensuing segments dark; in the fe- 

 males with a small transverse oval spot of salmon on each side of the 

 f orebelt, partly covered by the segment in front but showing through 

 its transparent margin, another similar spot behind it on the midbelt 

 (in alcoholic specimens the two spots appear more or less joined to- 

 gether) ; in the males the light spots of the midbody region are re- 

 duced in size, the anterior one sometimes missing on each segment, 

 and the coloration otherwise is less vivid than in the females, the males 

 being darker. Last segment with the exposed portion black, but on 

 each side there is a large salmon spot showing through the overlapping 

 penultimate segment. Behind segment 6 or 7 the ventral surface be- 

 comes increasingly lighter and is conspicuously salmon-colored on 

 the last segments. 



Head with a fine impressed median line on the vertex and another 

 on the clypeal region. Qypeus wnth four fovea on each side. 



First segment narrowly but evenly rounded on the sides, with a 

 broad, low raised rim. 



Ensuing segments with the transverse impression very faint on the 

 dorsum of all but six or eight of the anterior segments, where it is 

 marked by a very pronounced stria, which vanishes suddenly between 

 segments 7 to 10. Exposed portion of the anterior half of the seg- 

 ments with surface similar to the posterior half, being rather coarsely 

 reticulated and with a few fine scratches. Ventral striations not reach- 

 ing beyond the tips of the legs. 



Last segment with the tip usually exceeding the valves a little. 



Males with the first five pairs of legs considerably heavier than the 

 others, the sixth and seventh pairs intermediate in size. Legs 3 to 5 

 with coxae produced backward into broad, thick, rounded lobes ; those 

 of the fourth pair of legs a little larger than the others. 



