382 



U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



two semi-circular lips, an anterior and a posterior one, fringed upon their edge, and somewhat 

 raised above the surface of the chest. 



The dorsal fin exhibits two convex elevations, one anterior to the ven^, the other posterior to 

 it. Its continuity with the caudal is marked by a gradual shallow depression. The lower lobe 

 of the caudal is rather more developed than the upper lobe. The tail itself is bluntly spear- 

 shaped. 



The color is of a uniform chesnut tint, somewhat lighter along the abdominal region than over 

 the sides and back, which is much darker. 



List of specimens. 



2. ICIITHYOMYZON, HIRUDO, Grd. 



SPEC. CHAR. Head depressed, constituting the seventh of the total length, body and tail compressed, with irregular 

 transverse folds. Buccal disk sub-elliptical, provided with a crowded series of short tentacular fringes. Posterior margin of 

 buccal orifice exhibiting a series of seven teeth disposed upon an arc of a circle. Eyes small, inconspicuous. Spiracle 

 sub-tubular, raised above the surface of the cranium. Origin of dorsal fin nearer the apex of the tail than the anterior ex 

 tremity of the buccal disk. Vent placed opposite the most elevated portion of the dorsal fin. Gr yish brown above ; yel 

 lowish beneath. 



The head is longer than the chest; the tentacles are likewise more developed posteriorly than 

 anteriorly. The rounded edge of the lip, which borders exteriorly the shallow groove in which 

 the tentacles are inserted, is minutely scolloped, especially sideways. The branchial apertures 

 are vertically sub-elliptical, each provided posteriorly with a crescent shaped lip raised above the 

 surface of the chest, and fringed upon its edge. A few inconspicuous fringes are likewise 

 observed at the anterior edge of the same apertures. 



The portion of the dorsal fin anterior to the vent is somewhat convex in its outline ; imme 

 diately posterior to the vent it is the most elevated, diminishing again towards the upper lobe 

 of the caudal, into which it passes through a shallow depression. The upper lobe of the caudal 

 fin is rather deeper than the lower lobe ; the tail itself being posteriorly sub-elliptical in its 

 outline. 



The dorsal region is greyish brown ; the lower portion of the sides and the belly being of a 

 dull yellowish tint. 



List of specimens. 



