NATURAL SCIENCES OF PHILADELPHIA. 503 



Atherina sp. Forspalls. 

 Platycepbalus sp. Block, Schneider. 

 Sciena sp. Block, Schneider. 



Diagnosis. Rentes velutini. Pinna dorsalis prima spinis 11(12); secunda 

 et analis subasquales. Squamae mediocres, serie longitudinali 50 90. 



Body elongated and slightly compressed, rounded and widest on the back, 

 and more or less plane below. Scales on the side of moderate size, (50 90.) 

 Head elongated-conical, compressed, gradually and nearly uniformly narrowed 

 to the snout, which is horizontally rounded ; eyes moderate or large and sub- 

 median. Mouth small, the periphery of the jaws semi-oval; jaws subequal, or 

 lower shortest. First dorsal fin decreasing in a straight or convex line from the 

 front or anterior rays, and with eleven, rarely twelve, spines. Anal fin with two 

 slender spines, nearly equal to the second dorsal in extent and number of rays. 

 (D. I. 1723, A II. 15 23.) Caudal fins emarginated. Ventral fins with the 

 spine sometimes cartilaginous. 



Type. Sillago sihama, Riippell. 



Syn. Sillago acuta Cuv. 



Sillago is now restricted to the species having similar forms, scales of moderate 

 size and nearly equal dorsal and anal fins ; and it consequently excludes some 

 species that have been referred to it by previous naturalists, the Sillago punctatus 

 being taken as the type of one, and S. domina as that of another genus. Even in 

 the genus as now restricted, there are more considerable variations than are often 

 found in the same genus. While the ventral spine is slender, and, as usual, 

 osseous in most species, it is in one thick and cartilaginous. Again, some 

 species have cycloid scales in the cheek and forehead, while others have ctenoid. 

 The preoperculum is almost entire in some, while in others it is ciliated. A3 

 these differences do not, however, appear to be supported by others, they per- 

 haps can scarcely be regarded as generic, and the species so distinguished have 

 been therefore retained in the same genus. 



The following analytical table will exhibit the range of variation in the 

 genus, but, perhaps, is artificial, and may not show the affinities of all. 



I. Anal rays I. II. 1923. 



A. Ventral spine slender and osseous. 



a. Cheek and interocular scales cycloid, 

 b. Scales large, 50 55 along lateral line. S. macrolepis. 



bb. Scales moderate, 70 75 along lateral line. 

 Rows above lateral line 4, D. XL, I., 20, 21, A. I. 

 II. 22, 23. 

 Body and fins immaculate. S. sihama. 



Body immaculate; second dorsal spotted. S. malabarica. 



Rows above lateral line 5, 6. D. XI. I. A. I. II. 

 1921. 

 Body immaculate; dorsal spotted between rays. S. bassensis. 

 Back spotted. First dorsal brownish above, 

 dotted below ; second margined with 

 brown, and with two longitudinal vittae ; 

 caudal with three transverse orange vittas. S. maculata. 

 aa. Cheek and interocular scales ctenoid. 



Scales of lateral line 7075 ; above three rows. S. japonica. 

 Scales of lateral line 82 86; above seven rows. S. parvisquamis. 

 AA. Ventral spine thick and cartilaginous, united with the 



first ventral ray. S. chondropus. 



II. Anal rays II. 15, 16 (18 Cuv. et. Val.) 



First dorsal marbled with blackish ; second with four or 



or five rows of oblong spots. S. ciliata. 



1861.] 



