FISHES — GASTEROSTEIDAE — GASTEROSTEUS MICROCEPHILUS. 



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both edges, more conspicuously above than below, acerated upon its extremity, which either 

 reaches the tips of the ossa innominata or falls a little short of them. The formula of the fins' 

 rays has nothing peculiarly striking. 



D I, I, I, 12 ; A I, 9 ; C 4, 1, 5, 5, 1, 3 ; V I, 1 ; P 10. 



The upper surface of the head is corrugated ; the opercular, supra-scapular, and sub-orbital 

 bones exhibit radiating, sub-granular ridges. There are but three well developed plates, ex- 

 tending from the dorsal spines to the cubital process; a rather small one may be observed 

 anterior to these, and occasionally another, quite rudimentary. Their surface is minutely granu- 

 lar, the granules being disposed upon irradiating series, from a sub-central point corresponding 

 to the lateral line, which is not traceable beyond the plates. The skin covering the rest of the 

 body is perfectly smooth. 



The ground color is yellowish brown above ; the abdomen is silvery ; innumerable blackish 

 dots are scattered all over the head and body, more densely upon the upper regions, where cloud- 

 like spots may occasionally be seen, the result of the aggregation of those dots. 



All the specimens observed fall short of two inches, with the exception of one, which 

 measures two inches and four-tenths. They were collected in a fresh water lagoon, about one 

 mile back of Presidio on the bay of San Francisco. 



List of specimens. 



5. GASTEKOSTEUS MICROCEPHALUS, Grd. 



Spec. Ciiak. — Body partly plated ; peduncle of tail not keeled. Dorsal spines three, stoutish, slightly serrated upon their 

 edges ; Insertion of anterior one situated opposite the upper part of the base of the pectorals. Insertion of ventrals in 

 advance of second dorsal spine, their own spine being very large, serrated upon its upper edge, and extending beyond the 

 tips of the ossa innominata. Posterior margin of caudal sub-crescentic. 



Stn. — Gaslerosteus microcephalus, Gbd. Proc. Acad. Nat. Sc. Philad. VII, 1854, 133. 



In the fresh waters of the Tulare basin there is a species whose general aspect is entirely 

 different from any of those hitherto described from either California or Oregon. To those 

 acquainted with the eastern representatives of the genus, it will remind them of G. quadracus, 

 or apeltes, better than any others. It has the same sub-fusiform outline, great development of the 

 middle region of the body, tapering tail and diminutive head. The dorsal spines, the thoracic 

 plates, and the conformation of the ossa innominata, however, with other minor differences, 

 will be sufficient to distinguish the two species. 



The head is sub-quadrangularly sub-pyramidal, pointing forwards, and contained about four 

 times in the total length. Its upper surface is apparently smooth, but a magnifying glass shows 

 it to be finely granular. The eyes are large and circular; their diameter being contained three 

 times and a half in the length of the side of the head, exactly once in advance of the anterior 



