NATURAL SCIENCES OP PHILADELPHIA. 65 



The largest specimens which we have, so far observed, measure about two 

 inches in total length, the body tapering gradually away towards the insertion 

 of the caudal fin. The head, which constitutes the fifth of the entire length, 

 is subcorneal in general appearance, the snout being declivous and blunt and 

 overhangs the lower jaw. The anterior nostril is nearer the eye than the 

 margin of the upper jaw. The eye, itself, is large and subcircular, approxi- 

 mating the upper surface of the head ; its diameter enters nearly four times 

 in the length of the side of the head, twice behind its posterior rim and once 

 in advance of its anterior rim. The posterior extremity of the maxillar bone 

 corresponds to a vertical line drawn at the anterior rim of the orbit. The first 

 dorsal is convex in its outline, it is separated from the second by an appreci- 

 ciable space. The second dorsal, which is higher than the first, is longer than 

 high, its upper margin being subconvex anteriorly and nearly straight poste- 

 riorly. The caudal fin constitutes about the fifth of the total length. The 

 anal is longer than deep and nearly of equal depth throughout ; the vent, 

 which is placed close to its anterior margin, is opposite the origin of the second 

 dorsal. The insertion of the ventrals takes place in advance of the anterior 

 margin of the first dorsal ; they are slender and elongated, but their extremi- 

 ties are far from reaching the vent. The ventrals are well developed, posteri- 

 orly rounded, and project somewhat beyong the ventrals, being even with a 

 vertical line drawn at the terminus of the first dorsal fin. The formula of the 

 rays is as follows : D ix ; 14 ; A 10 ; C 4, 1, 7, 6, 1, 5 ; V i 5 ; P 13. The 

 ground color is yellowish with a triple series of blackish blotches, one along 

 the back, and one on either side immediately beneath the lateral line, which 

 runs along the sixth series of scales, counted from above. During life, 

 the intervening space between the lateral blotches is of a metallic green as 

 well as the cheeks. A black spot may also be observed upon the opercular 

 apparatus. A vertical black streak beneath the eye, and one on either side of 

 the snout. The dorsals, the caudal and pectorals are transversely barred with 

 black ; the anal and pectorals being unicolor. 



We propose calling this little fish Arlina effulgens in allusion to its bright 

 color during life. 



XVII. The Potomac river, in the neighborhood of Washington, has furnished 

 us with another representative of the Etheostomid family, of which constitutes 

 likewise a new generic type, related to Hadropterus and Hyostoma. It differs 

 from Hadropterus by the anal fin, which is smaller than the second dorsal, and 

 from Hyostoma by the contiguity of the dorsal fins. It is also allied to Boleo- 

 soma, from which it may be distinguished by a scaly throat and a truncated 

 caudal. The natural characters of this genus, to which we give the name of 

 Estrella, may be thus resumed. Body subfusiform and compressed. Head 

 subcorneal, well developed, rather blunt. Mouth of moderate size, somewhat 

 protractile, with its gape horizontal ; lower jaw shorter than the upper. Oper- 

 cular apparatus, cheeks and throat scaly. First dorsal fin nearly as high as 

 the second and contiguous to it. Anal smaller than the second dorsal. Cau- 

 dal fin truncated. 



The species is not uncommon, the largest specimens which we have ob- 

 served, measure about three inches and a quarter. The head forms a fifth of 

 the total length. The nape and occipital region constitutes an inclined plane 

 trom the orbits to the origin of the first dorsal fin. The eyes are very large, 

 fubelliptical in shape ; their horizontal diameter entering about three times in 

 she length of the sides of the head ; less than once in advance to the anterior 

 rim of the orbit. The posterior extremity of the maxillar bone extending as 

 far as a vertical line drawn in advance of the pupil. 



The first dorsal fin is much longer than high, superiorly convex, its mem- 

 brane being contiguous to the second dorsal. The latter is likewise longer 

 than high, but it is higher anteriorly than posteriorly, thus the upper margin 

 of that fin, which is subconvex or nearly linear, is nevertheless declivous 



1359.] 



