PROCEEDINGS OF THE NATIONAL MUSEUM. 529 



middle of its length. The terminal joint of tlie exopodite is about 

 two-thirds the length of the first joint, which bears eight or nine mov- 

 able sjiines. 



Varieties. — Animals answering to this description appear to be very 

 abundant in the Bay of Panama. There are three otlier groups of speci- 

 mens in the collection tliat are distinct from these, but the difterences 

 are so slight that they may all be regarded as varieties of one species. 

 First, there are a number of specimens from off Cape Lobos, Mexico, and 

 from Point San Ferrain to Consag Eock, Lower California, that are evi- 

 dently of the same species as those I have described as iS. panamensis, 

 but which differ from them in liaving the lateral spine of the fifth tho- 

 racic segment more curved and the anterior lateial carinje of tlie telson 

 produced into short spines, so tliat there are eight marginal spines on the 

 telson. This form may be designated as variety A. the Panama form 

 being taken as the type of the species. Variety B is represented by a 

 few specimens from the southeast of Tiburon Island, Mexico. It agrees 

 with the first in that the telson has but six marginal spines, while it 

 differs from this and agrees with the last in having a well-marked tooth 

 upon the outer side of the inner spine of the basal prolongation of the 

 uropod, and it differs from both theotheis m having the proximal seg- 

 ment of the exopodite not longer than the distal segment. The mar- 

 ginal spine of the fifth thoracic segment is large and curved forward 

 into a strongly sickle-shaped, acute process. The margins of the next 

 two segments are- rounded on the anterior side and have their points 

 directed farther backward, and are more sharply acute than in the 

 other varieties. This variety is also very different in its color markings, 

 if we may judge from alcoholic material. It is much less like the type 

 than variety J., and it may be found eventually to rank as a separate 

 species, for the only male specimens in the collection are very small and 

 immature, so that until adult males have been found we can not tell 

 whether or not this form possesses the characteristic tehon of 8. pana- 

 mensis. 



It is also with some hesitation that I refer to this species, a single 

 young male specimen from off" Cai)e Frio, Ihazil. In the shape of its 

 body, the arrangement of pigmented areas in the integument, and (he 

 form of its eyes it resembles <S\ panamensis very much, and the edge 

 of the telson appears to have begun to thicken, so it is probably better 

 to regard it as belonging to this species rather than to *S', empusa. If 

 this view be accepted this specimen will represent a thiid variety, G. 

 It differs from the type in having the rostrum elongated so that it 

 partly covers the ophthalmic segment. The anterior lateral spines of 

 the carapace are longer. The lateral angles of the second and third 

 exposed thoracic segments are longer and more acute. The first 

 abdominal segment carries lateral spines and the second one has inter- 

 mediate ones. Moreover, there is a good sized lobe on the outer side 

 of the inner spine of tlie basal prolongation of the uropod. 

 Proc. ^^. M. 04 34 



