ASTACIDJ2. 61 



vaJidOj lumine postico transversali, sulco antico longitudinal i, fere bi- 

 tuberculato. 



Long. corp. 3 ; antenn. 1.4 ; ped. antic. 1.9. 



Very old specimens : Long. corp. 4.7 ; antenn. 2.8 ; ped. ant. 3.5. 



Patria : Heading, Schuylkill River, Philadelphia ; Pittsburg, Pennsyl- 

 vania; New Jersey. Many very young specimens from the Niagara 

 and Lake Erie. The very old specimens from New York ; Havre de 

 Grace, Maryland ; from the Potomac at Washington ; Carlisle, Penn- 

 sylvania. 



The abdominal legs of the first form of the male vary a little in the 

 shape of the interior tip, which is more or less acute. I have fig- 

 ured both; the more acute one is taken from the largest specimens, but 

 it is also found in the younger. The obtuse tip is figured from one 

 of intermediate age. 



The young are similar to A. propinquas [vide that species). 



The full-grown and very old specimens, described by Mr. Girard as 

 Camharus Pealei, differ in the following points : — 



Mas. Corpore densius punctato-pubescente ; rostro latitudine duplo 

 longiori, leviter excavato, basi foveola lata, profundiori ; marginibus late- 

 ralibus inflatis, spinis anteapicalibus validis, subrejectis ; lamina anten- 

 narum margine externo subsinuato. Epistomate brevi, lato, antice ob- 

 tuso-rotundato, angulis lateralibus acutioribus. Thorace lateribus magis 

 granuloso ; cephalothoracis spinis acutioribus ; linea profunda, utrinque 

 fissa, spina duplici valida acuta aliisque minoribus ; spina antica infera 

 rejecta ; areola punctato-ciliata. Pedibus anticis validis ; chela forte 

 ciliato-punctata, margine interno subincurvo, dentato, supra et subtus 

 sulcato, digitis vix longioribus, planis, intus et digito mobili extus den- 

 tatis ; carpo spina interna media valida ; brachio spinis nonnullis ante- 

 apicalibus, nonnullisque minoribus anticis, omnibus acutis ; subtus 

 utrinque spina ad articulationem valida. Annulo feminse utrinque 

 tuberculo ad sulcum longitudinalem valido. 



Six very old and full-grown specimens from Havre de Grace, Mary- 

 land, agree so very well with the description given by Mr. Thomas Say, 

 that they are doubtless Astacus affinis Say. A full-grown male from the 

 Potomac, communicated by the Philadelphia Academy and labelled 

 " C. Pealei Girard?" is identical with the specimens from Havre de 

 Grace. Girard's species was from the Potomac, and " the fingers fasci- 

 ate with green near the tips " are also described by Mr. Thomas Say. 

 I have seen male and female from Reading, Schuylkill River, collected 

 by Professor Baird, labelled as C. affinis Girard, and communicated as 

 types from the Smithsonian collection by Professor W. Stimpson. The 

 male belongs to the second form ; the specimens are young, with only 

 one lateral thoracic spine ; in other respects they do not differ. I have 

 no doubt that they are young of the species described above ; Mr. Gi- 



