92 ASTACIDiE. 



2. AsTACUS NIGRESCENS Stimpson. 



Astacus nigrescens Stimpson, Proc. Boston Soc. N. II., T. 6, p. 87 (Separat p. 52). 



Figures on PL III. 

 Antennal lamina, fig. 168, a; epistoma, 6; spine of the second joint of the exterior antenna, e, 



Mas. Obesus, obscure olivaceus; rostro longo, valido, l);isi latiori, 

 antice fere parallelo, acumine triangular!, longiori acuto, subrecurvoj 

 supra medio canaliculato basi callo obsoleto in fovea antice angulata ; 

 tnarginibus calloso-inflatis, sex vel octo-tlentatis ; loco cretarum denti- 

 luis utrinque tribus acutis. Antennis validis, corpore brevioribus-, ar- 

 ticulis duobus basalibus dente externo acuto; antennis internis articulo 

 basali dente infero anteapicali acuto; lamina valida trigona, rostri 

 longitudinc, modice lata, margine externo crasso, inflato, apice spina 

 longa acuta. Epistomate lato, subtus carinato, antice triangulari ; pedi- 

 bus maxillaribus externis subtus spinulosis, intus barbatis. Thorace 

 ovato, depresso, densius et fortiter punctato, lateribus granulosis; linea 

 lata profunda, utrinque subsinuata; areola lata, plana, antice latius 

 dilatata. Postabdomine lato, fere laevi, segmentorum angulis externis 

 elongatis acutis; lamina media parte basali quadrangulari ; apice utrin- 

 que spinis duabus validis, subrejectis ; parte apicali minori, angustiori, 

 elliptica. margine antico exciso; lamina laterali vix costata, spina media 

 antemarginali, externaque marginali. Pedibus anticis validis, longis, 

 corpore paulo brevioribus; chela magna, elongata, subplana. margini- 

 bus subacutis, densius punctata, margine interim fere recto, subtus 

 paulo depresso ; digitis validis, rectis, chela? longitudine, conicis, apice 

 spinulosis. Carpo lato, granuloso, antice truncato, subtus spina media 

 valida. Bracbio la)vi, margine antico et superiori spinoso, spina apicali 

 majori, subtus biseriatim spinuloso, spina antica aliaque utrinque ad 

 articulationem majoribus. Pedibus abdominalibus, brevibus, rectis, 

 dimidio apicali cylindrico circumvolutis, apice truncatis. 



Femina differt ventre inter pedes quartos kevi, canaliculato ; annido 

 bifido laminato. 



(Maxim.) Long. corp. 4.6; antenn. 3; ped. antic. 4.2. 



Habitat : San Francisco, California. 



I have seen eight males and one female ; the fifth pair of legs has 

 branchiae. Male and female type communicated by Professor Stimpson. 



This species and A. GambeUi are separated from the others by the 

 denticulated rostrum. 



Cat. Xo. 228, San Francisco, Cal., Mr. T. G. Cary. Male. Spec. 4. 



Cat, No. 18-31, California, Mr. T. G. Cary. Male. Spec. 1. 



