51 



developed system of pores. In color it is not a very dark olivaceous 

 above, with bluish silvery reflections, becoming lighter posteriorly. 

 Each scale of the dark colored portion is darkest around its edges, 

 rendering the pattern of the scales very distinct. The color fades 

 into silvery on the sides, and silvery white below, with metalic 

 reflections, most evident on the base of the caudal. 



SUBCLASS GANOIDEI. 



The fishes constituting this subclass vary immensely in structure, so much so that almost 

 every genus constitutes a family, and every family is equivalent to an order; so much so that 

 our leading systematists are divided in their opinions as to the limits of the subclass, and have 

 weighted the world with arguments to prove that the curious mud-fishes {Lcpidosiren and Pro- 

 topteriis) of South America and of the Gambia belong to it, and vice versa; and so nruch so that 

 some have even suggested the dismembering of the subclass, considering the differences in struc- 

 ture among its members to outweigh the resemblances. All agree, however, in the importance 

 and great extent of the structural peculiarities of each group; although the characters they pos- 

 sess in common are two only, the arterial bulb (of the heart) with several rows of valves, and 

 optic nerves which do not simply cross, but form a chiasma. In common with the sharks and 

 rays, they have lieterocercal tail, that is a tail with the upper lobe, containing a prolongation of 

 the vertebral column, longer than the lower, which is developed below it like a second anal fin ; 

 the air bladder differs in structure in the various groups, and the bony or ganoid enamelled 

 plates which charactei'ize some of the more typical form are wanting in others. 



The only ganoid fishes found on this coast belong to the chondrostei or cartilaginous ganoids, 

 or, which is the same thing, to the family Acipenseridce or sturgeons. The skeleton is cartilag- 

 inous, five longitudinal rows of bony shields run along the elongate, subcylindrical body; the 

 toothless mouth is a transverse slit on the under side of the head, in the same position as that 

 of the shark ; in front of the inouth are four barbels; and the dorsal and anal fins are set far 

 back. There are no gill rays or branchiostegals ; a large air-bladder, and the intestine has a spiral 

 valve. The species are numerous; three or four occur on this coast, but only one is brought to 

 our markets in quantity. 



Acipenser brachyrliynchus, Ayres, Sturgeon — This is the only species 

 of sturgeon which is brought to market in abundance, as the fisher- 

 men have a prejudice against the long-nosed or green sturgeon, Aci- 

 penser acutirostris, Ayres, which is abundant in the bay and the rivers 

 and creeks flowing into it, asserting that it is poisonous. Acipenser 

 brachyrliynchus is always in season, and always abundant, the weight 

 of its flesh sold in the markets probably exceeding that of any other 

 single species, excepting, perhaps, Oncorhynchus quinnat. It attains 

 a very large size. On February 25th of this year I measured an 

 individual 9' 9" long, the weight of which was- 427 pounds. But 

 even this was exceeded by a specimen brought to the California 

 Market Christmas, 1878, measuring nearly twelve feet in length and 

 weighing about 600 pounds. Examples of this size are of course 

 rare. Caviare is manufactured in considerable quantities from the 

 roe. Dr. Ayres describes a third species, Acipenser medirostris, but I 

 have not yet recognized it. 



SUBCLASS ELASMOBRANCHII. 



The animals belonging to this class are commonly called fishes, but are distinguished by so 

 many peculiarities of structure that they may be regarded ns a subclass. This subclass con- 

 tains the sharks, the rays, and the Chimaroids, examples of each of which groups may be 

 found upon our coast. 



In these fishes the skull is formed of cartilage alone, and no membrane bones (such as the 

 parietal, frontal, etc.) are develo]3ed in relation to it; the gills are not free; the branchial open- 

 ings are slit-like, and, (except in the Holocephali, or Chimceroids), several in number, there are no 

 scales, but the external hard parts are what is known as placoid, composed of calcified papilla; 

 and the eggs are few and large; some are ovo-viviparous. The minute structure of these pla- 

 coid points or scales is precisely the same as that of teeth, which are also dermal in their origin. 

 In the Holocephali the upper jaw and its suspensorial cartilages are wanting in a separate con- 

 dition, as the parts representing them are united into a continuous cartilaginous plate, which is 



