^00 [September, 



Descriptions of new species of Astacus from Georgia. 



By John Le Conte. 



A few years ago there were but three or four species of this genus known to 

 inhabit the United States ; lately Mr. Girard, in the proceedings of this Society 

 vol. vi. page 86. has increased the number to eighteen or nineteen ; but one 

 however is from the South, A. Blandingii. I now add to this number eight more : 

 two of them from the upper part of the State of Georgia, the rest from the low 

 country. There are two more species which I have seen, but have not been able 

 to obtain. What number of species are found in the rivers of the South is not 

 yet ascertained. All those which I have seen were inhabitants of ditches, ponds 

 and rivulets of clear water, or formed burrows in the mud of wet ground. Their 

 extreme similarity renders it difficult to distinguish the species from each other, 

 and this difficulty will undoubtedly increase as the number of species is multi- 

 plied. To what extent this number may reach cannot be guessed at ; it appears 

 however that when these animals come to be more closely studied, this number 

 will be very great, and the passage of one species into another become almost 

 imperceptible; so that among Crustaceans we shall have an analogous difficulty 

 to that which exists among Uniones. Their color is generally lost with their 

 life, so that it is of little value in the description. All that I have ever seen 

 were much of the same color, a reddish-brown, inclining to a dark olive. The 

 shape of the rostrum and of the chelae and the size of the Areola vertebralis, afford 

 the best characteristic marks. I have never known this last character to vary in 

 any degree. In the two others there may occur slight differences of develope- 

 ment, not however so great as to be of any moment. I do not find that any 

 marks can be definitely pointed out, by which we can distinguish those which 

 are subterranean from those which are aquatic. 



A. troglodytes. Rostrum paulo concavum, obtusiusculum cum acumine 

 parvo, utrinque unidenticulatum, qui denticulus obtusus est, saepius obsoletus. 

 in junioribus magis conspicuus. Lamina antennalis subdolabriformis, peduncu- 

 lum aatennalem sequans. Cephalothorax grosse et sparse punctatus, lateribus 

 antice et postice paucigranulosis ; linea ordinaria sulcata. Thorax supra grosse 

 et sparse punctatus, lateribus granulosis, granulis interdum vix conspicuis. 

 Areola suturalis medio angusta. Dorsum grosse et parce punctatum. Chela 

 magna, lata, evasa, tuberculata margine interiore dentata ; digiticostati asquales. 

 punctati basi tuberculati, interior concavus, exterior convexus. Carpus latere in- 

 terno spinis dentiformibus, numerosis, spina media majore. Brachium margine 

 superiore serratum, superficie inferiore lineis duabus spinularum, antice utrin- 

 que spina longiore. Caudoe lamellae intermedin pars anterior utrinque trispinosa. 



Long. 3.1. Cephalo-thorax 1.16. Thorax .6. Abdomen 1.4. Cauda .54. 

 Antennae 3. Chela 1.5 lat. .55, forceps .9. 



Habitat in Georgian oryzaceis, ubi spiracula 4 unc. alta format. 



A. Blandingii. Rostrum concavum acuminatum, versus apicem vix utrinque 

 unidenticulatum, sed lateribus subcontinuis ad acuminis extremitatem. Lamina 

 antennalis subdolabriformis, pedunculum antennalem aequans. Cephalothorax 

 et thorax supra punctati latioribus granulosis, hie spina parvae medio marginis 

 lateralis ; linea ordinaria non sulcata. Areola suturalis angusta. Dorsum 

 glabrum seriebus parvispunctorum transversalium. Chela longiuscula, angusta. 

 subcylindracea, punctata cum granulis : digiti aequales. Carpus extus punctatus ; 

 intus granulatus, granuli quidamanteriores quinque aut sex spiniformes. Brachi- 

 um extus glabrum, intus parte anteriore granulosum, saperficie inferiore lineis 

 duabus granulorum acutiorum, vel spinarum parvarum. Caudae lamellae inter- 

 mediae pars anterior utrinque bispinosa. 



Harlan, Trans. Am. Phil. Soc. 3, 464 ; Med. and Phys. Res. 229, pi. fig. 1. 



Cambarus Blandingii Er. Wiegm. Arthiv, 1846, 1,98. Girard, Proc. Acad. 

 6, 91. 



Long. 3.5. Cephalothorax 1.16. Thorax .6. Abdomen 1.2. Cauda .54. 



Habitat in Georgiae et Carolina regionibus intermediis. 



