ASTACIDiE. 41 



long) ; the female is smaller. The first abdominal leg of the male, 

 figured by me after the type, shows exactly the shape of the male 

 full-grown Forma II., but not as well finished as it is always found 

 in the young specimens. I have not seen a similar young specimen 

 from New Orleans ; the smallest is 2.6 una long, but agrees very well. 

 The young of C. troglodytes, of which I have seen specimens 0.6 una 

 long, are very similar; but C. Clarldi differs in having the rostrum exactly 

 triangular and a little attenuated at the tip (it is more dilated, with the 

 margins curved, in C. troglodytes) ; the acumen is longer, more acute 

 (in 0. Clarldi type z \ una left side, j\ right side) ; the basis of the ros- 

 trum has two obsolete elevations connected in an obtuse angle ; the 

 lamina of the antennad is more elongated, smaller at the tip. 



In the Museum of the Natural History Society of Boston are two 

 females, together with a great number of apparently very young ani- 

 mals, before described by me. 



Cat. No. 1162, New Orleans, La., L. Agassiz. Mas. Form I. and II. 

 Fern. Spec. 12* 



Cat. No. 166, New Orleans, La., L. Agassiz. Mas. Form I. Fern. Spec. 5. 



Cat. No. 264, New Orleans, La., Mr. Allen. Mas. Fein., young. Spec. 3. 



Cat. No. 1822, Mobile, Ala., L. Agassiz. Mas. Form II., young. Spec. 2. 



3. Cambarus troglodytes LeConte. 



Astacus troglodytes LeC, Proc. Acad. Pliilad., T. 7, p. 400. 



Figures on PI. I. and III. 

 First abdominal legs of the male : 



first form, fig. 1 1 in front, fig. 1 2 outside. 



second form, fig;. 13 in front, fig. 14 outside. 

 Antennal lamina, fig. 141, a ; epistoma, b ; spine of the second joint of the exterior antenna, c. 



Mas. Kostro triangulari, lato, tertia parte longiori, subdeflexo, ante 

 apicem acutum, brevem, paulo barbatum, utrinque leviter sinuato ; supra 

 fere piano lcevi, utrinque subtiliter marginato, tuberculo obsoleto piano 

 in foveola basali orbiculari ; cretis basalibus extus sulcatis, apice 

 subacutis, subparallelis. Antennis gracilibus, corpore paulo breviori- 

 bus, articulis duobus basalibus dente externo parvo subacuto ; antennis 

 internis articulo basali dente infero medio acuto; lamina externa 

 rostro longiori, articulo antennarum tertio vix breviori, lata, apice vix 

 rotundata, margine externo inflato, apice brevi spinoso. Epistomate 

 lato, antice et utrinque subsinuato (forma variabili, semper brevi, 

 lateribus obliquis). Pedibus maxillaribus intus et basi subtus villosis. 

 Thorace postice latiori, postice subdepresso, granuloso, cephalothorace 

 medio fortius punctato, postice obsolete bicalloso, linea modice pro- 

 funda et sinuata, lateribus fissa, spina infera ad antennarum basi apicali 

 acuta ; areola media angusta, subcarinata, postice latiori, transverse 



