Jordan and Evermann. — Fishes of North America. 751 



Represented iu coastwise streams of California and northward by 



nOla. (USTEBOSTEUS WILLIAMSON! MICROCEPHALUS (Girard). 

 (California Stickleback.) 



Head 3 to ?>\ ; depth 3 to 3f ; eye 4 ; snout 3i. Dorsal II-I,. 11 ; anal 

 I, 8. Body short, deep, moderately compressed. Caudal peduncle rather 

 deep, not compressed, nor evidently keeled. Processes from shoulder 

 girdle below widely diverging, leaving a triangular area on breast; 

 naked area in front of pectorals smaller than in cataphractii.s. Dorsal 

 spines stout, about as long as from tip of snout to pupil ; third dorsal 

 spine and anal spine small ; ventral spines stout, about equaling distance 

 from tip of snout to posterior rim of orbit, strongly serrate on outer 

 side and with a distinct basal cusp; ventral plate shorter and broader 

 than in cataphractus, about half as wide as long. Lateral armature 

 variable ; plates usually 5 or 6, but sometimes completely armed with 25 

 or 26; all intermediate numbers occasionally found, the anterior plates 

 large, these followed by smaller ones; the posterior half usually 

 unarmed ; often the plates are reduced to one or two, or even entirely 

 absent, especially in brook specimens ; often again the whole length of 

 the body is provided with plates, the jiosterior ones quite small, consid- 

 erably smaller than corresponding plates in cataphractus, but forming a 

 distinct keel. Usually specimens from the same stream are alike or 

 nearly so, the variously armed forms having the nature of local varieties. 

 The fully armed variety abounds in San Gregonio Creek, Pilarcitos Creek, 

 and other streams of the west slope of the Sierra Morena, on the San Fran- 

 cisco peninsula. Olivaceous, silvery below ; skin thickly punctulate ; 

 males blackish in spring, with coppery or golden luster. Pacific Coast 

 of the United States, in streams and brackish waters; abundant south- 

 ward, ranging from Alaska to Todos Santos in Lower California. Proba- 

 bly an offshoot from Gasterosteus cataphractus, but now apparently entirely 

 differentiated. We have seen no intermediate forms, the fully mailed 

 examples having smaller plates * than in Gasfcrostcus cataphractus. (fiiKpoc, 

 small ; Kefa?,//, head, but the head is unusually large for a stickleback.) 



Gasterosteus microcephalus, Girakd, Proc. Ac. Nat. Sci. Phila., 1854, 133, Four Creek (Kaweah 



River), a tributary of Tule Lake (Tulare Lake) San Joaquin Valley, California; Jordan 



& Gilbert, Synop.sis, 395, 1883. 

 Gasterosteus plebeius, Gibard, and Gasterosteus irwjiiiiatus, Girarp, 1. c., 147, Presidio, 



California. 

 Gasterosteus puijetti, Gibard, Proc. Ac. Nat. Sri. Phila., 1856, 135, Fort Steilacoom; Puget 



Sound. 



* " In Gasterosteus microcephal us, the number of lateral plates varies from to 25 (excluding the 

 keel). Where the larger number ia present, they extend from the head to the keel on the cau- 

 dal peduncle. When only the smaller number, they are above the ventral fins. The posterior 

 plates are more likely to be absent than the anterior ones. The variations do not seem to bear 

 any relation to the character of the stream, for in one of two similar streams DC per cent, were 

 found to be fully plated, while in the other none had more than seven plates. In another 

 stream an e(]ual number of each sort was taken. The number bears no relation to age. The 

 caudal keel is, with scarcely au exception, confined to the fully mailed individuals."' (Oloudsley 

 Rutter, MS.) 



