FISHES OF THE FAMILY LORICARIID®, 263 
9. Hypoproroma. 
Hypoptopoma Giinth. Proc. Zool. Soc. 1868, p. 234. 
Oxyropsis Eigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 1889, p- 39, and Occ. Pap. Cal. Ac. i. 1890, 
p- 387. 
Body moderately elongate ; snout margined with recurved spines; eyes placed very 
low, equally visible from above and below ; interoperculum a plate on the lower surface 
of the head; temporal plate not perforate; teeth slender, bifid. Dorsal above, or a 
little behind, the ventrals, with I 7 rays, anal with I 5, pectoral with I 6, ventral 
with 15; caudal emarginate ; adipose fin, if present, represented by a feeble spine. 
Vertebre 5+6+15 (in H. guentheri); ribs absent. 
Amazon and La Plata Systems. 
Key to the Species. 
I. Pectoral spine extending to middle of ventral; abdomen with 3 longitudinal series of 
plates. 
Depth of body 54-5} times in its length; caudal peduncle slightly 
compressed, 34 times as long as deep . Mpa 1. H. thoracatum Gthr. 
Depth of body 7} times in its length; caudal peduncle depressed, 
i/ WES OS ONS AYO) 5 6 6 o 6 6 es a 6 5 6 b oe BE JEL Gopi Stale 
If. Pectoral spine extending to posterior end of ventral or beyond; abdomen with 2 series of 
plates, separated anteriorly by a single median plate. 
A. A transverse series of 4 plates in front of the clavicles. 
1. Caudal peduncle 3} times as long as deep; pectoral spine not extending to origin 
of anal. 
No adipose fin ; length of head nearly 3 times in the total length (in 
arspecimen! Of Gapmm:) Or 9. seer 5 cw) ne are Gaede Quentnenn Blogs 
An adipose fin; length of head 2? times in the total length (in a 
Saou OE AT) Gg ot Be oe Gg eh FR li Wen: 
2. Caudal peduncle 2% times as long as deep; pectoral spine 
extending to origin ofamal . . . . . . . =. =. +. 5. A. steinduchneri Bier. 
B. A single plate in front of the clavicles . . . . . . . 6. H. gulare Cope. 
1. HypopropoMa THORACATUM. 
Hypoptopoma thoracatum Giinth. Proe. Zool. Soc. 1868, p. 234, fig. 2. 
Hypoptopoma bilobatum Cope, Proc. Am. Phil. Soc. xi. 1870, p. 566, figs. on p, 567. 
Depth of body 54-5} times in the total length, length of head 34 times. Diameter 
of eye 53-6 times in the length of head, interorbital width 13-1} times. Occipital 
region evenly convex, without distinct median ridge. Scutes spinulose, not carinate, 
23-24 in a longitudinal series. Lower surface of head with a naked area in front of 
VOL, XVII.—PART 111. No. 10.— October, 1904. 2N 
