0(18 t'ROCEEDIXaS OF TBE XATIOXAL MUSEUM. 



First abdominal somite devoid of appendages in both sexes; podo- 

 brancliii^^ lacking a bilobed plaited lamina, altliougli the stem may be 

 expanded into a wing; epipod of first maxillii)ed generally furnished 

 with branchial filaments, coxopoditic seta' hooked at the end; telson 

 not divided by a transverse suture. 



ASTACOIDES Guerin. 

 Jstacoides Gkkkix, Revue Zoologique, II, p. 109, 1839. 

 Tyix', Axiacokhs goudotii Gnorin=./s/rtti(s madai/ascarioisis Audonin et Milne-Edwards. 



nostrum short, quadrilateral, concave above, margins furnished with 

 small teeth or tubercles. Antennal scale verj^ small." Anterior process 

 of epistome long triangular. Superior border of the hand dentate. 

 Sides of the carapace armed with small tubercles, some of which assume 

 the form of small spines. Number of well-developed gills reduced to 

 twelve on each side of the body; jiosterior arthrobranchiu' rudimentary 

 and functionless ; one pair of pleurobraiu-hia^ (on the fourteenth somite) ; 

 the branchial formula, according to Huxley,- being as follows : 



Arthrobranchi;e. 



Somite. rononKANCHi^E. . Pleurobranchi^.. 



Anterior. Posterior. 



VII. . . . O(opr) . . . . . . . . . . = O(epr) 



VIII. ... I ....»■.... .... = 1 + r 



IX. ... 1 .... 1 .... .... =2 



X. ... 1 .... 1 ....»•.... = 2 + r 



XI. ... 1 .... 1 ....'•.... = 2 + )- 



XII. ... 1 .... 1 ....»■.... = 2 + r 



XIII. ... 1 .... 1 ....'■.... = 2 + r 



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



6_|.ep)- + 5-f/- + 4r + 1 = 12 + 5r + epr 



One species known. 

 Habitat. — Mad agascar. 



ASTACOIDES MADAGASCARIENSIS (Audouin et Milne-Edwards). 



AstacHS madar/ascariensis Audouin kt Milne-Edward.s, Jonru. de I'lnstitut, 1839, 



p. 1.52; Artli. du Mas. d'Hist. Nat., II, ]). 35, pi. in, 1841. 

 Astaco'ides oondotii Gukrix, Revue Zoologique, II, p. 109, 1839.^ 

 Astacm (Astaco'idcs) madafjascarknsis EricH!>os , Arch. f. Naturgesch., 12ter Jalirg., 

 I, p. 89, 1846. 



'Erroneously said to be wantinor by Guerin. 



-Proc. Zool. Soo. London, 1878, p. 775. 



■"Guerin's description of the Madagascar crayfish must have been publLshed about 

 the same time as Audouin and Milne-Edwards's. The Revue Zoologique was issued 

 monthly. Guerin's description occurs in the April number, 1839. Audouin and 

 Milne-Edwards's description in the Institute, p. 1.52, was communicated to the 

 Societe Philomatique on the 27th of April, 1839. In cases like this it seems reason- 

 able to retain the name adopted by the next following author who treated of the 

 species — in this instance, Audouin and Milne-Pidwards -n the Archives du Museum 

 d' Histoire Xatnrelle, II, 1841. 



