CRUSTACEA OF ALABAMA. 



4* 



This peculiar species was described by Say, in 18 18, but seems to have been con- 

 stantly misunderstood. It was figured by Bate, from specimens of doubtful origin under 

 a new name. From any species known to the writer it can be distinguished by the sharp 

 spinous processes of the dorsal margin of each of the first three abdominal segments. 

 Bates' specimens had the last thoracic segment carinate also. This may be sometimes 

 the case in our species, though not in observed specimens. 



Description of female. Length about eight centimeters, rather graceful ; eyes 

 elongate, sub-reniform ; upper antennae over half as long as body, flagellum considerably 

 longer than peduncle, over fifteen-jointed, secondary flaggellum short, three-jointed ; 

 lower antennae much shorter, flagellum seven- or eight-jointed, peduncle longer than 

 that of first antenna, the second segment being longest ; first leg shorter than second, 

 propodos oval, twice as long as broad, palmar portion indistinct, dactyl curved, rather 

 short ; propodos of second leg about the same size, but obovate and obliquely truncate ; 

 natatory legs long ; the sides of the second and third abdominal segments produced and 

 toothed below these segments with the first carinate above and produced backward into 

 strong acute spines much more prominent than in Allorchestes dentata ; sides and top 

 of the fourth, fifth and sixth abdominal segments with the usual clusters of spines ; base 

 of pleopod of the fourth abdominal segment very long, rami of all pleopoda unequal, 

 spinous ; divisions of telson slender, spiny tipped. 



Gammarus (Gammarella?) dubius, s P- »■ 



(Plate VI, Fig. 1.) 



Two imperfect specimens, apparently from the Gulf of Mexico, differ from the genus 

 Gammarus in several respects. 



About 14 mm. long; compact; eyes circular, antennae long, with very stout basal 

 joint ; peduncle rather short, flagellum (unknown) probably of moderate length, second- 

 ary flagellum very short, two-jointed ; lower antennae with long peduncle ; coxae of ante- 

 rior limbs moderately expanded; gnathopoda subequal, anterior propodus quadrate, 

 large, strongly armed upon the palmar surface, with a strong spine above the base of the 

 strong dactyl ; second propodus similar, palmar surface oblique, armed as in the preceed- 

 ing ; legs sub-equal ; pleopoda very spiny, short, basal joint of second pair very short 

 and broad, third pair uni-ramose, terminal joint sublamellate ; telson apparently double, 

 but really single, with two quadrate portions twice as long as wide, separated by a deep 

 incision ; abdominal segments without tbe spines characteristic of Gammarus. It seems 

 probable that this species should belong in Melita or Gammarella, but it differs in not 

 having the quathopoda unequal. The species is variously banded and ornamented. 



