SOUTH AMERICAN NEMATOGNATHI. 253 



temporal, to which the stay is firmly joined. Snout very long and 

 pointed; head compressed; lower profile straight, upper profile strongly 

 arched. Humeral process broad, rounded behind. Numerous pores in 

 the axil, giving a sieve-like appearance. (HASSAR.) 



I. A conspicuous black spot on the dorsal fin composed of small dots; 

 scapula covered with skin. orestes 20C. 



II. Dorsal dusky at tip, without a black spot; scapula granular. 



affiinia 201. 



189. Hemidoras nattereri, 



Oxydoras nattereri Steiiidachner, Flussfische Siidamerika's, ii, 4, 



pi. 2, figs. 1-la, 1881 (Teffe, Amazons). 

 Hemidoras nattereri Eigenm. & Eigeiim. Proc. Cal. Acad. 2d Ser. i, 



158, 1888 (Coary; Jutahy; Teffe). 

 Habitat: Solimoens. 



Body short and deep, compressed, the ventral outline 

 almost straight, dorsal outline strongly arched, highest 

 in front of the dorsal spine. Head short, somewhat 

 deeper than wide, its depth being about equal to its 

 length: the opercle, preopercles, suborbitals, prenasals 

 and entire upper surface of the head striate, becoming 

 reticulate posteriorly. In the adult the snout is entirely 

 covered with ossifications except a curved oblong area 

 connecting the anterior and posterior nares. Interor- 

 bital region flattish, occipital region steeply roof-shaped. 

 Fontanel an oval opening somewhat shorter than the 

 eye, situated in a groove about as long as the eye, en- 

 tirely surrounded by dermal ossifications. 



Eye large, 1-1J in the snout, 2f-3 in the head, -1 in 

 the interorbital. 



Barbels all connected by a membrane; those of the 

 maxillaries extending to below the eye, with a few cirri 

 on the outer margin; a 5th and 6th barbel arise on 

 either side of the symphysis and extend outward to the 

 edge of the membrane. 



Gill-opening extending forward to below the eye. 



Coracoid process exposed, striate. Humeral process 

 broad and long, reaching to below the 2nd or 3d dorsal 

 ray, its surface granular, obliquely truncate behind. A 



