100 THE VOYAGE OF H.M.S. CHALLENGER. 



"1. PsammyUa littoralis. Longer aniens doubly than the liead, short anteus not longer than 

 their first segment ; last pair of feet double in length ; body rufous above, white beneath. — 

 Obs. I have found this animal in great numbers on the shores of Long-Island and New- 

 York, and on the Hudson river, jumping about like fleas, whence its vulgar name Sand-flea ; 

 it jumps by means of its hind feet and tail, like locusts. Length about half an inch, often 

 less ; eyes large and round. 



" IV. Pepheedo. (Natural order and family of the foregoing.) The two upper antens longer 

 and with six long segments ; all the feet with one nail, and nearly equal, the two first pairs 

 with thick swelled hands ; body without lateral appendages, tail with simple filaments. — 

 Obs. This genus was noticed in my Analysis of nature, and formed on an European 

 species ; the name is mythological. It may be deemed a singularity in this family, that 

 this genus should be a freshwater one, and the last a land one ! 



"1. Pephredo liotamocjeti. Long antens, scarcely longer than the head and double of the short 

 ones ; body fulvous, transparent, with a central brown or longitudinal stripe. — Obs. It 

 lives on the Potumogeton perfoliatum in the Hudson and the Fishkill, near Newburg. 

 Length three lines, creeper, eyes very small." 



PsammyUa littoralis is obviously one of the Orchestidse, a " beach-flea." The upper and lower 

 antens of Rafinesque's terminology would be respectively the lower and upper antennae of 

 ordinary language. If the two genera PsammyUa and Pephredo, covdd be identified, they 

 might probably enough fall as synonyms to others already known. It is possible that the 

 acute American observers of the present day will be able to identify the two species here 

 given with some that have been since named. 



1817. Say, Thomas, bom 1787, died 1834 (Hagen). 



On a New Genus of the Crustacea, and tlie Species on which it is established. 

 Read July 8, 1817. Journal of the Academy of Natural Sciences of Philadelphia. 

 Vol. i. Part 1, No. 4. August 1817. Philadelphia, 1817. pp. 49-52. 



The new genus Cerapus, assigned to the order Macrouri, is thus defined : — "Essential Character. — 

 Thumb of the second pair of feet bi-articulate ; interior antennse four-jointed, exterior ones 

 five-jointed. Artificial Character. — Antennae subequal, interior ones 4-jointed, exterior 

 ones 5-jointed. Two anterior pairs of feet monodactyle, the second pair with a two- 

 jointed thumb. Natural Character.- — Body semicylindrical, somewhat linear, decreasing 

 towards the tail, ten-jointed. Head distinct from the first joint and larger, quadrate, a 

 little elongated into an angle near the base of the interior antennaa, each side, for the 

 reception of the eyes, which are hardly prominent. Antennae nearly equal, very large, 

 interior ones with the first joint thick, second and third nearly equal ; exterior antennae 

 five-jointed, the first joint placed in a deep sinus beneath the eye, short, not projecting 

 beyond the margin of the head above, second joint hardly longer than the first, third and 

 fourth equal to the second and third of the interior antennae. Anterior pair of feet 

 moderate, with a small ovate hand and moveable nail, not closing on the hand, attached to 

 the first segment of the body ; second pair with the basal joint attached to the edge of the 

 body (as in Cymothoa, &c.), second joint broad, compressed, with an incisure near the base 

 before, third small, medioliform, carpus cylindrical, narrower than the preceding joint ; 

 hand very large, compressed, subtriangular, attached to the carpus by the inferior edge of 

 the acute angle, which is a little curved, tip emarginate and armed with a strong, acute 

 spine on the anterior angle, thumb two-jointed, first joint incurved, linear, second acute, 

 closing on the spine of the hand. Third and fourth j)airs of feet equal, similar to each 



