402 [September, 



aut granuiis, excepto margine interiore qui paucis denticulis inconspicuis in- 

 structus est, digiti recti puactati carinati. Carpus glaber, punctis tribus vel 

 quatuor. Brachium glabrum, spinulis paucis latere superiore: inferiore seriebus 

 duabus spiuarum, quarum duee anteriores majores et longiores. Cauda? lamella 

 intermedia utrinque trispinosa. 



Long. 1.95 Cephalo-thorax .6. Thorax .25. Abdomen .8. Cauda .3. An- 

 tenna .9. Chela .6. latitud. .2, forceps .3. 



Habitat in Georgia inferiore, in aquas puras rivulos qui inter colliculos arenosos 

 {sand-hills) currunt. 



A. latimanus. Rostrum breve, concaviusculum, obtusum cum acumine parvo. 

 Lamina anteunalis brevis subdolabriformis, pedunculi antennalis articulum in- 

 feriorem solum asquante. Cephalo-thorax supra punctatus, lateribus granulosis, 

 linea ordinaria sulcata. Thorax supra punctatus, lateribus valde granulosis, 

 areola suturalis modica. Dorsum sicut in aliis. Chela magna, latissima, extrorsum 

 marginata, grosse punctata, ad latus internum tuberculata, digiti sequales, recti, 

 late costati, punctati, interiore extrorsum et introrsum, exteriore introrsum 

 tuberculato. Carpus punctatus, latere interiore tuberculatus, spina satis magna 

 e medio prominente. Brachium punctatum, latere superiore bi-vel-trispinosum, 

 spinis parvis, inferiore spinarum seriebus duabus. Lamella caudse intermedia 

 bispinosa. 



Long 3.3. Cephalo-thorax 1. Thorax .6. Abdomen 12. Cauda .5. Antenna 

 2.6. Chela 1.2, latit. .65 forceps .6. 



Habitat in Georgia superiore. 



A. advena. Rostrum subconcavum, breve, obtusum cum acumine parvo. 

 Lamina antennalis parva, articulum pedunculi antennalis inferiorem solum 

 aequans. Cephalo-thorax supra grosse punctatus, lateribus granulosis. Areola 

 suturalis angusta. Dorsum sicut in aliis. Chela breviuscula, latiuscula, tuber- 

 culata, margine exteriore et interiore serrata, digitis carinatis, punctatis. Carpus 

 grosse punctatus, latere interiore spinoso-tuberculatus. Brachium latere supe- 

 riore, serie unica spinarum parvarum, quae sensim deorsim diminuuntur, infe- 

 riore seriebus duabus spinarum parvarum. Cauda? lamella intermedia utrinque 

 bispinosa. 



Long. 2.9. Cephalo-thorax .9. Thorax .5. Abdomen 1.3. Cauda .4. An- 

 tenna 1.5. Chela .85. lat. 4. forceps .45. 



Habitat in Georgia inferiore. 



Hyeme vitam degit subterraneam. ^Estate in fossis invenitur. Differt a 

 praecedente magnitudine ; chela non marginata et digitis non tuberculatis, ex- 

 cepto margine interiore digiti interioris. 



In all the species of this genus which have come under my observation, I have 

 observed that the following characters are found. The lamina antennalis is 

 dolabriform, inwardly fringed, outwardly thickened, straight and ending in a 

 small spine. The dorsum is smooth with transverse rows of punctures. The 

 carpus has a deep longitudinal impression. The males also have on the second 

 and third of the small legs a tooth directed inwards, in some species only on the 

 second. 



In drawing up these descriptions it will be observed that I have preserved the 

 old name of Astacus in preference to the new appellation of Cambarus. The 

 very slight and not very apparent differences which have been adopted to dis- 

 tinguish these two genera appear to me of little moment. 



On a new species of Gelasimus. 



By John Le Conte. 



One species only of Gelasimus ha9 long been known as an inhabitant of our 

 salt marshes. I now offer to the Society, the description of a second species, 

 found on the sea coast of New Jersey. It seems hitherto to have escaped the no- 



