A Revision of the Genus CovyJoras. 209 



Fiff. 5. Spines on terminal joints of leg-. 



JFig. 6. Dorsal view ; walkinpf-legs removed. 



Fiff. 7. Terminal joints of ovigerous leg. 



Fi(/. 8. Spine of oviger. 



Fiff. 9. Palp. 



FiQ. 10. Chela. 



Fiff. 11. Oviger with egg-mass. 



XXIV. — A Revision of the South- American Siluroid Fishes 

 of the Genus Corydoras, loitha List of the Specimens in the 

 British Museum [Natural History). By 0. Tate IIegan, 

 M.A. 



(Published by permission of the Trustees of the British Museum.) 



The Callichtbyid fishes with the occipital process extendinf^ 

 to the plate at the base of the dorsal fin-spine may be divided 

 into two genera — Corydoras, Lacep., 1803, with 6 to 8 soft 

 rays in the dorsal and the base of tiie fin about equal to its 

 distance from the adipose fin_, and Brochis, Cope, 1871, with 

 9 to 11 soft rays in the dorsal fin, which is more extended, its 

 base considerably more than its distance from the adipose 

 fin. In his recent list of Neotropical fishes Eigenmann 

 recognizes the genus Osteogaster, C'ope, including therein two 

 species which have the humeral shields somewhat larger than 

 usual. One of these is a Corydoras, viz. C. eques, Steind,, 

 which is closely related to C. nattereri and still more closely 

 to C. macrosfeus, described below as new; the other is of a 

 very different type, and sliould, in my opinion, be placed in 

 the genus Brochis ; it is B. .tj)lendens, Casteln. 



There are so many species of Corydoras unrepresented in 

 the British Museum collection and of uncertain position that 

 I find it difficult to make a satisfactory key to the species. 



Synopsis of the Species. 



I. Interorbital width -| the length of head or less ; snout more than ^ 



the length of head. 



Scutes in upper lateral series 23 1. treitlii. 



Scutes in upper lateral series 26 or 27 2. kronei, 



II. Interorbital width | the length of head or more. 



A. A series of spots along the side and a second series on the back. 



1. Diameter of eye 6 or 7 in length of head. . 3. micracanthus. 



2. Diameter of eye 4 or 5 in length of head. 



Head Sf in tlie length 4. microcephcdm. 



Head 3j to Z\ in the length 5, paleatus. 



3. Diameter of eye 3|^ in length of head .... G. yarbei. 



J 



