EEPOET ON THE AMPHIPODA. 103 



1818. Say, Thomas. 



An Account of the Crustacea of the United States. Eead July 7, 1818, 

 Jourual, &c., pp. 374-401. 



Say here describes tlie new sjiecies Gammarus fasciatus from the rivers, Gammarus minus, found 

 in brooks under stones, Gammarus mucronatus, Gammarus appendiculaius, ■which has 

 " caudal segments, and three te7-minal seginents of the body, dentated on their posterior 

 edges." " The remarkable elongation of the inner lamella of the second pair of feet in one 

 sex [9] is a very striking peculiarity of this species." " It is probable," he adds, " that 

 this animal -n-ill form a new or subgenus, which would very probably arrange under Gam- 

 marus." Spence Bate leaves the name unaltered, but says, " Certainly it does not belong 

 to Gammarus. It appears to be related to Podoeerus." It is more suggestive of Msera. 



The new germs Le^ndactylis is thus described: — "Essential character. — Antennx four-jointed, 

 furnished beneath with plumose cilice, intermediate ones with an accessory seta placed at 

 tijj of the third joint. Clypeus i^roduced between the bases of the intermediate antennfe, 

 and acute. Feet, two anterior pairs simple, equal, third and fourth subeqiial, didaotyle, 

 fingers lamelliform ; remaining feet spinous, without nails. Natural character. — Body com- 

 pressed-oval. Head distinct, subquadrate, extended into a short acute rostrum between 

 the intermediate antennas ; antennx subequal, four-jointed, inferiores rather longer, incurved, 

 second and third joints dilated beneath, compressed, and ciliated beneath with plumose, 

 elongated hairs, these two joints, when at rest, form a continued oval, the former is dolabri- 

 form, terminal seta eight-jointed, verticillate, superiores porrected, basal joint dilated, 

 depressed, second one much smaller, placed on the inner tip of the preceding, and with that 

 joint furnished with plumose cilise beneath, third joint much smaller than the second, and 

 furnished at the tip with a tri-articulate accessory seta, parallel with the terminal joint ; 

 terminal joint of about eight segments, and not longer than the preceding joints conjunctly ; 

 eyes convex, touching the anterior edge of the head ; thorax with seven segments, and 

 lateral scales ; feet fourteen, two anterior pairs in each sex simple, filiform, equal, third 

 and fourtli pairs equal, didactyle, hands compressed, not dilated, finger rounded, thumb 

 oval, lamelliform, remaining feet gradually larger, compressed, armed with short spines, and 

 destitute of a nail ; hind pair largest, antepenultimate joint lengthened above, and nearly 

 attaining the tip of the following joint, which is crenate and spinous on the edge, terminal 

 joint compressed, serrated, and spinous on the edges, and truncate at tip ; anterior pairs of 

 feet furnished at their inner bases, with oblong oval moveable lamellse. Abdomen of three 

 segments, abruptly narrower than the thorax, each furnished beneath with natatory feet, 

 consisting of short, rounded peduncles, supporting double setse, of which the outer ones are 

 longest, third segment abruptly inflected at tip; tall inflected, armed with bifid styles." 

 The species Lepidactylis dytiscu.^ has " Eyes orbicular ; body when recent, white, with an 

 abbreviated internal ferruginous vitta, including the alimentary canal ; accessory seta of the 

 intermediate antennae, attaining the tip of the fourth segment of the terminal joint ; anterior 

 pairs of feet hairy. Length, male one-quarter, female three-twentieths of an inch." In 

 shallow pools left by the receding tide "its presence may be ascertained by the numerous 

 and irregular tunnels which it forms in the sand, like miniature representations of those of 

 the mole, only less rectilinear." It is the same as Oniscus arenarius. Slabber. See notes 

 on Slabber and P. L. S._ Miiller. 



To the genus Ampithoe, Leach, Say assigns the new species Ampithoe serrata and Ainpithoe 

 punctata from Egg-harbour, and Ampithoe dentata, " a very common inhabitant of the 

 freshwater marshes of South Carolina." Ampithoe serrata is thus described: — "antennx 

 equal, short, stout ; eyes large, approximated, suboval ; eighth, ninth, and tenth segments 



