90 



U. S. p. R. R. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



As regard to tlio plates on the sides of tlie body, tlieir number and arrangement is the same 

 as in the preceding species. 



The ground color of the dorsal region is greyish, rendered almost black by crowded dots of 

 the latter hue ; tlie sides are lighter and silvery. The base oftiie caudal fin is marked by a 

 transverse jet black band, sometimes reduced to two patches, one to cither lobe. 



List of specimens. 



4. GASTEROSTEUS INOPINATUS, G r d. 



Spec. Char. — Body partly plated ; peduncle of tail consequently not keeled. Dorsal spines three, slender, £md slightly serrated 

 upon their edges, insertion of the anterior one taking place above the base of the pectorals. Insertion of ventrals placed imme- 

 diately in advance of the second dorsal spine ; ventral spine serrated on both edges, but less conspicuouslv below tlian above, and 

 its extremity terminating about evenly with the tips of the ossa inno^ninala. Posterior margin of caudal fin sub-crescentic. 



Stn. — GasUrosteus inopinalus, Grd. Proc. Acad. Nat. Sci. Philad. VII, 1854, 147. 



In many respects this species might be considered more closely allied to G. phheius than either 

 G. serratus or G. intermedius. In the first place, the anterior or thoracic region alone is plated ; 

 the insertion of the ventrals in advance of the second dorsal si)ine is another similarity between 

 it and G. plcbeius. 



The general aspect is slender, elongated, considerably tapering from the origin of the anal 

 backwards ; the peduncle of the tail especially is long and slender. The greatest depth of the 

 body, measured across the origin of the ventrals, is contained five times in the entire length. 

 The head itself constitutes the fourth of the same length. 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, exactly 

 once in advance of their anterior rim. The mouth is somewhat smaller'tban in G. plebeius, 

 er[ually oblique, but the lower jaw is less protruding beyond the upper. 



The anterior dorsal spine, which is inserted immediately above the base of the pectorals, does 

 simply reach the base of the second spine when brought horizontally backwards. Furthermore, 

 there are instances in which it docs not extend even so far. The tip of the second spine leaves 

 quite a space between it and the third spine. The spines themselves are very slender and acute, 

 and not, or but slightly, serrated upon their edges. The origin of the second dorsal takes i)laco 

 quite posteriorly to a vertical line intersecting the tips of the ossa innominata. The beginning 

 of tlic anal is situated opposite the fifth or sixth soft ray of the second dorsal, tlie middle rays 

 of both of these fins being bifurcated. The posterior rays terminate evenly, at a considerable 

 distance from the base of the caudal fin. The anal spine is very exiguous. The caudal fin, which 

 constitutes the seventh of the total length, is concave posteriorly, composed of ten bifurcated 

 and two undivided rays, with rudimentary ones above and below. The insertion of the ventral 

 spine takes place immediately in advance of the second dorsal spine ; it is minutely serrated on 



