172 BULLETIN 2 01, UNdTEiD STATES NATIONAL MUSEUM 



12, 1882, 3 specimens ; Woods Hole, V. N. Edwards collector, surface, 

 evening, May 2, 1888, 1 adult female ; Woods Hole, 1 adult female, 2 

 adult males, 16 immature; ? Puerto Eico, S. T. Danforth collector, 

 2 adult females, badly damaged and dry at some time ; the following 

 material was identified by S. I. Smith : Provincetown* ; Woods Hole* ; 

 Casco Bay* ; Noank* ; Vineyard Sound* ; Speedwell stations 56-58*, 

 65-66*, 994*; Dr. Mary J. Rathbun identified material from Anti- 

 costi*, St. Pierre Harbor, Newfoundland* ; Casco Bay* ; A. E. Verrill 

 identified material from Casco Bay* ; Vineyard Sound*. 



Distribution. — The known distribution of this species extends from 

 the littoral waters of the Gulf of St. Lawrence to the coast of New 

 Jersey. Records from farther south are lacking, probably because 

 very little collecting has been done on the more southerly coasts of 

 eastern North America. It is therefore all the more regrettable that 

 the specimens from Puerto Eico here doubtfully recorded as belonging 

 to this species are in such a poor state of preservation that certain 

 identification is precluded. If correct they represent the most south- 

 erly record for the species and suggest that it is probably to be found 

 all along the eastern coast of North America. It would be interesting 

 to have the southern limits of its distribution determined. 



Remarks. — This species is very closely allied to M. mixta, and young 

 specimens of both species are very difficult to separate. I am not sure 

 that I have successfully accomplished this separation in the records of 

 both species I have given here. Adult specimens are more easily dis- 

 tinguished. Smith (1879) summarized the distinguishing features of 

 the two species as follows : 



Antennal scale : M. mixta (fig. 63, a) , nine times as long as broad ; 

 outer margin nearly straight. M. stenolepis (fig. 64, a) 12 times as 

 long as broad ; outer margin concave in outline. 



Antennular peduncle: M. mixta, penultimate joint one-third 

 longer than the ultimate. M. stenolepis, penultimate and ultimate 

 joints subequal. 



Telson: M. mixta (fig. 63, d), cleft much deeper than in M. steno- 

 lepis; spines of the lateral margins more than 30 extending almost to 

 the distal end, at least three or four on the margin posterior to the base 

 of the cleft. M. stenolepis (fig. 64, d), spines on the lateral margins 

 about 25, the posteriormost spine at about the level of the base of the 

 cleft, so that there is a considerable unarmed posterior portion of the 

 lateral margins. 



Smith also points out differences in color between the two species, 

 M. stenolepis possessing many more chromatophores than M. mixta. 



Of the differences pointed out by Smith, the telson is the most readily 

 observed in preserved material. I give here figures of the telson and 

 antennal scale for comparison with those of M. mixta as given in Sars' 



