152 Proceedings of the Biological Society of Washington. 



These two small aquarium fishes were presented to the American 

 Museum of Natural History by Mr. William Mack, of New York. There 

 was no accompanying data, but they are probably South American, and 

 are referred to the genus Ccelurichthys of Ribeiro.* 



Ccelurichthys tenuis sp. nov. 



The type No. 4087, American Museum of Natural History, is a speci- 

 men 31 mm. long to base of caudal; depth, 4.0 in this measure; head, 

 4.1 ; eye, 3.0 in head; snout, 4.0; end of maxillary from tip of snout, 

 2.3. Elongate and compressed, the dorsal outline almost straight; the 

 ventral outline arched downward in front and slanting gently upward 

 behind. Lower jaw projecting. Maxillary vertical, to front of pupil. 

 Snout short. Nostrils separated by only a narrow partition. Pores on 

 side of head above. Dorsal origin equidistant from base of central caudal 

 rays and posterior margin of gill-cover. Its height only slightly less than 

 the length of head. When depressed, the dorsal overlaps the front of 

 the adipose fin. Anal long, its origin distinctly in advance of that of the 

 dorsal. Ventrals to anal. Pectorals past base of ventrals. Caudal 

 broad ; this fin is broken but was certainly forked, perhaps with a rounded 

 lower lobe. A peculiar scaly, downward opening, pocket structure on the 

 base of the middle caudal rays. Dorsal 9, anal 32. Scales 40, about 13 

 lengthwise series. Lateral line incomplete, short, on about 7 scales. 

 Lower jaw with a single row of cusped teeth in front, changing abruptly 

 to minute teeth on the side. Upper jaw with what apparently is a single 

 row of cusped teeth, about 3 small teeth at the side beyond the premax- 

 illary-maxillary angle, t t ill membranes separate and free. A broad 

 dusky, lengthwise band on the lower part of the side, a narrow central 

 streak above it posteriorly. Central caudal rays and tip of lower jaw 

 more or less dusky. 



Our only other specimen, American Museum of Natural History No. 

 4088, 32 mm. long., has 31 anal rays and apparently an imperfect inner 

 row of teeth in the front of the upper jaw ; otherwise resembles the type. 



These two small Aquarium fishes were presented to the American 

 Museum of Natural History by the New York Aquarium Society. There 

 was no accompanying data. They are close to Ccelurichthys lateralis. 



The two species here described may be separated from C. iporangx as 

 follows : 



Depressed dorsal not reaching adipose. Lower 



caudal lobe pointed. Depth 3.5 lateralis 



Depressed dorsal reaching adipose. 



Depth 3.5 , iporangse 



Depth 4.0 tenuis 



s 



* Rio de Janeiro, Kosmos, V, No. 2, February, 1908. 



