130 BULLETIN 138, UNITED STATES NATIONAL MUSEUM 



Genus ASTACUS Fabricius, Milne Edwards 



Astacus Fabricius, Syst. Entoin., 1775, p. 413 (part). 



Astacus Milne Edwards, Hist. Nat. Crust., vol. 2, 1837, p. 329; type, A. 

 astacus (Linnaeus). 



Body robust and ovate; first pair of abdominal appendages of 

 male neither bifid nor toothed at tip ; no hooks near base of any of 

 thoracic legs. 



The last thoracic somite bears a pleurobranchia on each side, the 

 full number of gills being 36; there are besides two or three rudi- 

 mentary gills on each side of body; the hindmost podobranchia is 

 provided with a plaited, bilobed lamina, like those in front. The 

 orifice of the green gland is situated on posterior face of tubercle. 

 The annulus ventralis is represented by a transverse ridge behind 

 the penultimate thoracic sternum. 



Miocene; Pliocene; Recent. 



ASTACUS CHENODERMA Cope 



Plate 29, fig. 7 ; plates 31-34 



Astacus chenoderma Cope, Proc. Amer. Philos. Soc., vol. 11, (1870) 1871 

 p. 606 ; type-locality, Catharine's Creek, Idaho ; topotypes in U. S. Nat' 

 Mus., Cat. No. 353343 (Smithsonian No. 9779) ; cotypes perhaps not 

 extant. 



Astacus breviforceps Cope, Proc. Amer. Philos. Soc, vol. 11. (1870) 1871, 

 p. 606 ; type-locality, Catharine's Creek, Idaho. 



Carapace (pi. 31, fig. 1; pi. 33, fig. 3) : Surface finely wrinkled; 

 numerous granules or small tubercles with anterior openings for 

 insertion of hair. In cases where the surface has been worn and the 

 granules obliterated or partly so, the punctae appear larger on an 

 otherwise smooth surface. Cervical suture verv deep. Grooves on 

 either side of the cardiac region far apart. A^blunt median carina 

 on the anterior portion of the carapace is continued for a short dis- 

 tance on the basal portion of the rostrum, diminishing in width an- 

 teriorly. Rostrum (pi. 33, figs. 1 and 3; pi. 34, figs. 1 and 2) long, 

 diminishing gradually to a point, bordered on each side by a strong 

 carina, Avhich is roughened by unequal and unevenly spaced tuber- 

 cles up to the number of seven ; the carina is continued behind the 

 line of the orbit. Outside this portion of the carina and wholly 

 behind the orbit there is an obliquely longitudinal line formed by 

 two teeth or tubercles the posterior slope of which is elongate 



Abdomen (pi. 29, fig. 7; pi. 32; pi. 33, fig. 5) : Surface similar to 

 that of the carapace but with the tubercles and their punctae more 

 numerous. When the surface is a little worn the punctae are much 

 more conspicuous. First somite short, produced laterally in a slender 

 pleuron. Second somite twice as long as the first, its pleuron sub- 



