FISHES — GASTEROSTEIDAE — GASTEROSTEUS WILLIAMSONI. 



93 



Oregon. In its general appearance it resemWes G. microcephalus most, and what has just been 

 stated in regard to the latter, with reference to G. quadracus, applies equally to it. 



It is much to our regret that the state of keeping of the specimens will not permit a thorough 

 description of the soft fins. The species differs from G. microceplialus by a larger head, much 

 smaller spines, and fewer plates upon the thoracic region. The head enters three times and a 

 half in the total length ; the eyes are circular and very large, since their diameter enters but a 

 little over three times in the length of the sides of the head, and not quite once in advance of 

 tlie anterior rim of the orbit. The dorsal spines are slender, acute, and smooth upon their 

 edges ; the anterior one is inserted immediately behind a vertical line drawn across the base of 

 the pectorals. In being brought horizontally backwards, its extremity would hardly reach the 

 second dorsal spine ; the latter, at any rate, remains considerably behind the third in that 

 respect. The origin of the second dorsal is even with a vertical line passing by the extremity 

 of the ossa innominata. The insertion of the ventrals is entirely in advance of the second dorsal 

 spine ; their spine exhibits a very slight serrature upon its edges, and its extremity extends 

 beyond the tips of the ossa innominata. 



The plates or shields are but four in number, occupying the space between the first and second 

 dorsal spines. The three longest converge towards the vertical process of the ossa innominata. 



The ground color is brownish, rather dark along the dorsal region ; the sides are transversely 

 barred with black, the bars or bands being composed of crowded dots. The belly is unicolor. 



The largest specimens measure an inch and a quarter. 



List of specimens. 



7. GASTEROSTEUS WILLIAMSONI, Grd. 



Spec. Char. — Body smooth all over ; peduncle of tail not keeled. Dorsal spines tliree, exiguous and slender, and not serrated ; 

 insertion of anterior one situated above the base of the pectorals. Insertion of ventrals slightly in advance of tlae second dorsal 

 spine ; their own spines are serrated upon both edges, and their extremities do not reach the tips of the ossa innominata. Posterior 

 margin of caudal fin sub-crescentic. 



Syn. — Gasterosteous williamsoni, Grd. Proc. Acad. Nat. Sc. Philad. Vll, 1854, 133. 



This is the most slender, and, consequently, the most elongated and graceful of all the species 

 of the genus above described. The body is sub-fusiform in profile, and, as usual, compressed. 

 The greatest depth, taken across the base of the pectorals, is a little more than the fifth of the 

 total length. The upper surface and the sides of the head are corrugated, the head itself 

 forming the third of the total length, the caudal fin excluded. The eyes are large and circular, 

 and their diameter is contained three times and a half in the length of the sides of the head. 

 The mouth is slightly oblique and the lower jaw longer than the upper, the free extremity 

 of the maxillary extending to a vertical line intersecting the nostril. 



