NATURAL SCIENCES OF PHILADELPHIA. 171 



Among the Arii, with six barbels, there are apparently, thirteen generic 

 types, Galeichthys Val., Hexanematichthys Bleeker, Leptarivs Gill, Guiritinga 

 Bleeker, Cephalocassis Bleeker, Hemiarius Bleeker, Ariopsis Gill, Notarius JGill, 

 (=Arius Bleeker, 1862, nee 1858), Netuma Bleeker, Ariodes M. T., Sciades M. T., 

 Arms Val., Bleeker, 1859 (Pseudarius Bleeker, 1862,) and Genidens Cast. 



Bleeker, in his first systematic revision of the Siluroids, restricted the name 

 Arius to the genus of which the Arius arius Val. is the type, and, although it 

 might have been advisable to have retained it for the first group, as be subse- 

 quently did, it must now be preserved with the limits assigned in 1859. His genus 

 Arius, of 1862, comprises two distinct types, one with the buckler oblong, re- 

 presented by the Arius grandicassis, which may be called Notarius, and the 

 other with the buckler transverse, already named Ariopsis. 



Leptarius Down Gill. 



Extreme length (5-f inches) 100 



Body. Greatest height 10 



Height at ventrals 8 



Height of tail behind anal fin 5 -J 



Least heightof tail 5 



Length of tail 17 



Head. Greatest length 19 



Distance from snout to nape 



Greatest width 13 1 



Width of interorbital area 5 



Length of snout 6 



Length of maxillary barbels 30 



Length of outer chin barbels 12 



Length of inner chin barbels 10 



Orbit. Diameter 31 



Dorsal. Distance from snout 25* 



LeDgth of spine 71 



Greatest height 1~-\-x. 



Length of base 7 



Anal. Distant from snout 55 



Length 13 



Height at longest ray 71 



Caudal. Length 13 



Length of middle rays 6 



Pectoral. Length ju 



Length of spine 10 



Ventral. Distance from snout 42 



Length 7 



Genus SCIADES Mull, and Troschel. 

 Sctades Troschelii Gill. 

 The greatest height is contained about 4| times in the length to the base of 

 the caudal fin, and 5J times in the total. The caudal peduncle, behind the 

 anal, equals the interval between the snout and the eye, and its least height 

 that between the centre of the anterior nostril and eye. The head in front and 

 on the sidt-s is smooth, and a smooth, oblong triangular area extends nearly to 

 the vertical from the upper angle of the preoperculum ; a triangular area on 

 each side is incurved externally to the narrow anterior extremity, and covered 

 with white pisiform granulations. The dorsal buckler is a pentagon, with a 

 semi-circular excavation behind and with its surface rugose. The head enters 

 three times in the length before the end of the anal fin and more than four 

 times in the total ; its width equals the interval between the snout and upper 

 angle of preoperculum, and the interocular area equals half the head's length. 

 1863.] 



