232 PROCEEDINGS OF THE ACADEMY OP 



illary batbels extend three-fourths the distance to the opercular border ; outer 

 (longer) mentals scarcely beyond middle branchiostegal angle. Height of body 

 at base of dorsal equal three-fourths length of head. End of pectoral oppo- 

 site posterior border of first dorsal, its spinous ray serrate ; ventrals not 

 reaching anal. Basis of anal terminating a little behind base of adipose ; 

 length of caudal peduncle below, equal length of pectoral spine. Rays D. 

 1 7 ; P. 19 ; V. 8; A. 18 ; C. 16. Spine of dorsal smooth. Caudal openly 

 emarginate, the emargination much above the middle rays, giving the highest 

 a short lobate outline. Lateral line straight to scapular angle, mouth of 

 axillary mucous duct distinct. Length of head 2 in. 8 1. ; width below 2 in. 

 '2, 1. : from muzzle to base of ventrals 4 in. 3 1.; to base of caudal 7 in. 9 1. ; 

 length of caudal 1 in. 7 1. ; another specimen is about ten inches in length. 

 The color of the upper surfaces, tail, fins, barbels and under jaw is black ; 

 sides varied with dirty yellow , abdomen and thorax yellowish-white. J. 

 Stauffer informs me that the dark pigment of the skin of this animal comes 

 off upon the hands in handling it. A specimen died in twenty minutes after 

 capture, when put in water, though uninjured ; the Ameiiri, like other Cat- 

 tish, will live for many hours after complete removal from their element. It 

 is occasionally caught by fishermen, and is supposed to issue from a subter- 

 ranean stream, said to traverse the Silurian limestone in that part of Lan- 

 caster county, and discharge into the Conestoga. 



Two specimens of this fish present an interesting condition of the rudi- 

 mental eyes. On the left side of both a small perforation exists in the co- 

 lium, which is closed by the epidermis, representing a rudimental cornea ; 

 on the other the corium is complete. Here the eyeball exists as a very small 

 cartilaginous sphere with thick walls, concealed by the muscles and fibrous 

 tissue attached, and tilled by a minute nucleus of pigment. On the other the 

 sphere is larger and thinner walled, the thinnest portion adherent to the cor- 

 neal spot above mentioned ; there is a lining of pigment. It is scarcely col- 

 lapsed in one, in the other so closely as to give a tripodal section. Here we have 

 an interesting transitional condition in one and the same animal, with regard 

 to a peculiarity which has at the same time physiological and systematic sig- 

 nificance, and is one of the comparatively few cases where the physiological 

 appropiiateness of a generic modification can be demonstrated. It is there- 

 fore not subject to the difficulty under which the advocates of natural selection 

 labor, when necessitated to explain a structure as being a step in the advance 

 towards, or in the recession from, any unknown modification needful to the ex- 

 istence of the species. In the present case observation on the species in a 

 state of nature may furnish interesting results. In no specimen has a trace 

 of anything representing the lens been found. 



I am indebted to the same enterprizing Society and its Secretary for another 

 inhabitant of the Conestoga, which has hitherto escaped the notice of zoolo- 

 gists. This species, which has been distinguished by Jacob Stauffer in corres- 

 pondence, is an Etbeostoma,* one possessing the character of the genus in a 



* A species of the allied genus Poecilichthys in the Mus. Academy Nat. Sci., from the Platte 

 River, near Fort Kearney, Nebraska, presented by Dr. Hammond, appears to have been as yet un- 

 d escribed. It may be called P. mesaeus. A stout, little compressed species, with large scales. 

 Dorsals not in contact. Eye entering live times into length of head, more than once in muzzle 

 anterior to its border; head 4J^ times in total length. Caudal very rounded; first scarcely a8 



4 



high as secjnd dorsal. Pectorals longer than ventrals, not reaching vent. Scales 40. Fin rays 



5 

 D. ix 13; P. 10: V. 14; A. 9; C. 2141. Outline of back rather elevated. Length 2% 

 inches. Beside the large size of the scales, the proportionally longer head and fjur soft ventral 

 rays distinguish it. from other species. The color in spirits is pale brown, with four dorsal blotches, 

 and a few groups of zigzags on the sides. Second dm sal and caudal barred. 



The collections also contain a series of species of Hulolepis, which dill'tr as follows, one being 

 apparently undescriued: 



[Oct. 



