244 PATAGONIAN EXPEDITIONS : ZOOLOGY. 



Skin covered with minute cirri or papillae, which are especially con- 

 spicuous over the humeral region and head, the tail sometimes smooth. 



Distance of dorsal fin from tip of snout 2f-2f in the length, the spine 

 stout and smooth, li-if in head. Distance of the adipose fin behind 

 the dorsal about equal to the length of the adipose fin or one-half longer, 

 5-6 in the length. 



Caudal emarginate, with numerous, short, accessory basal rays. 



Free margin of the anal straight or slightly convex, the fifth ray highest, 

 about 1 1 in the head, rapidly decreasing to the last ray, which is about 

 half the height of the fifth. 



Pectoral spine very strong and with a leathery prolongation ; height of 

 the spinous portion if-2 in the head; outer margin of the spine smooth, 

 inner margin with strong, recurved teeth along its entire length. 



Bases of all the fins, lower part of head, suborbital regions and opercles 

 and a median line on the back purplish ; rest of body and fins yellowish 

 and under the lens dark. 



Head 4-4!; depth 4^-5*; Br. 7 ; D. I, 7 or 8 ; A. 9-12. 



No specimens were collected by Hatcher and the above description is 

 based on the material in the Museum of Comparative Zoology at Harvard 

 University. 



Family III. PYGIDIID^. 



>Siliiyoidei tyichomycteriformes Bleeker, Nederl. Tijdschr. Dierk. I, 112, 



1863. 

 >Sihiridce opisthoptercB Giinther, Cat. Fish. Brit. Mus. V, 4, 1864. 

 >Sihtridce branchicolcB Giinther, 1. c. 



> TricJwinycteridcE Gill, Arrangement of Families of Fishes, 19, 1872. 

 = Pygidiidcs Eigenmann & Eigenmann, Am. Nat. July, 1888, and South 

 Amer. Nematognathi 316, 1890. 



Distribution of the species : East and west slopes from Colombia to 

 La Plata and along the Andes to Patagonia. 



Air-bladder vestigial, part on either side of the coalesced vertebras and 

 enclosed in a capsule formed by the lateral processes of the coalesced 

 vertebrae only ; the external orifice of the air-bladder capsule as in Hyp- 

 ophtJialmidcE, its anterior side closed. Adipose fin none ; dorsal usually 

 on the caudal, sometimes on the abdominal portion of the vertebral 

 column ; anal short. Derm naked. Dorsal and pectoral spines scarcely 

 developed. 



