NO. 1136. OBSEE VATIONS ON THE ASTA CIDJE— FAXON 671 



The telson of the specimen figured by Heller is more spiny tlian usual. 



This species was first described by Shaw as Cancer serratus, a name 

 already used by Forskal for a different animal, Scylla serrata. Follow- 

 ing the American Ornithologists' Union Committee's code of nomencla- 

 ture, 1 the name serratus must be discarded in favor of spinifer of Heller. 



The number and arrangement of the gills are the same as in A. 

 franklinii, as shown in the formula on page 669. But the inner wall 

 of the stem of all the podobranchise, except the hindmost, develops 

 a broad limb or ala, as in the genus Cheraps; this ala, however, bears 

 long hair-like setse in place of the hooked branchial filaments seen 

 in Cheraps. In A. franlclinii this ala is very rudimentary, in which 

 regard that species shows again its affinity to Astaco'ides madagasca- 

 riensis. The epipod of the first maxilliped bears a large number of 

 bookless branchial filaments. 



Genus CHERAPS Eriehson. 

 Cheraps Euiciison, Arch. f. Naturgesch., 12ter Jahrg., I, p. 101, 1846. 

 Type, Astacus ( Chcrapa) preissii Eriehson. 



Eostrum rather narrow, triangular, plane or even a little convex 

 above, obscurely margiuate, entire or obscurely toothed near the tip. 

 Antennal scale broadly oval, or often broadly truncate at the distal 

 end. Anterior process of epistome broadly triangular. Superior border 

 of hand with a denticulated carina. Carapace and abdomen smooth, 

 nearly free from spines and tubercles; areola narrow. Distal moiety 

 of telson and of both branches of the posterior abdominal appendages 

 membranaceous; median carina of inner branch of the latter terminat- 

 ing in a small spine near the middle of the segment; transverse suture 

 of the outer branch halfway between the proximal and distal ends. 

 Form cambaroid. Gills forty-two (one pair very small — almost rudi- 

 mentary), disposed as shown in the following table: 2 



Aetheobbanchle. 



Somite. Podobeanchlss. , Pleurobeanchl*;. 



Anterior. Posterior. 



VII. . . . 0(epr) . . . . . . . . . . = .0(epr) 



VIII. ... 1 .... 1 .... .... = 2 



IX. ... 1 .... 1 .... 1 .... =3 



X. ... 1 .... 1 .... 1 .... =3 



XI. ... 1 .... 1 .... 1 .... 1 =4 



XII. ... 1 .... 1 .... 1 .... 1 =4 



XIII. . . . 1 . . . . 1 . . . . al . . . . 1 =4 



XIV. ...0....0 0....1 =1 



6+epr +6 -f- 5 + 4 = 21+epr 



a Very minute, almost rudimentary. 



Habitat. — Australia. 



1 Cauon XXXIII. 



2 The arrangement and structure of the branchial apparatus in Cheraps was first 

 described by Huxley, from an undetermined specimen in the British Museum from 

 the Yarra-Yarra River, Australia. From the locality, this specimen was presumably 

 Cheraps Mcarinatus. I have examined the branchial organs in specimens of C. hicar- 

 Inatus in the Museum of Comparative Zoology and find that they agree in every 

 respect with Huxley's description (Proc. Zool. Soc. London, 1878, pp. 768, 769, fig. 

 6). Eriehson was manifestly wrong in saying that Cheraps, like Cambarus, lacked 

 gills on the last thoracic somite. 



