170 II. S. p. R. R. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



scales of unequal size, tapering posteriorly to but one series. On the middle of the abdomen 

 they are sensibly larger than elsewhere, and upon the post pectoro-ventral region they are alto- 

 gether out of proportion with the rest. Opposite the base of the anal fin they are smaller and 

 irregular ; they likewise diminish in size towards the belly and chest. As to their structure, 

 tlie figures given will speak for themselves : a little longer than high, witli the posterior margin 

 regularly convex, the anterior margin truncated, and the superior and inferior edges sub-linear 

 or slightly curved. 



The ground color appears to have been dark purplish brown, deeper in the female than in the 

 male, in which it has a tendency to a more olive hue, with diffused darker spots or blotches. 

 The spinous portion of the dorsal fin, the extremity of the caudal, and the pectorals, are rather 

 yellowish, whilst the soft portion of the dorsal, the base of caudal, the anal, and the ventrals, 

 are uniformly deep purplish in the female, lighter in the male, in which a yellowish elongated 

 spot is observed at the base of the posterior extremity of the dorsal. The head presents the 

 same tint as the body. 



While in the immature state of growth some individuals of this species exhibit, sometimes, 

 transverse greyish bands across the body, less distinct, however, on the belly than on the back. 

 A light vitta may likewise be seen extending along the base of the anal fin for nearly its whole 

 length, and disappearing almost entirely in large specimens. 



The female genital apparatus of the specimen figured was found to consist of an elongated, 

 tubular, membranous sheath, extending from the thoracic belt to the vulva. To the upper roof 

 of the sheath are firmly attached some highly vascular membranes hanging downwards, and 

 dividing the whole tube into elongated pouches or compartments. Five of these vascular membranes 

 were found to be present, and by an attentive examination it was soon discovered that they were 

 in fact the true ovaries, two in number, as required by the law of symmetry : the right ovary 

 being composed of three membranes, and the left of two only. Consequently the right ovary 

 had two pouches or partitions, and the left only one. Upwards of sixty young were found in 

 these organs ; about an equal number in each ovary ; a few more, however, in the right-sided 

 one. 



The young (Plate XXVI, figs. 3 and 4), from six to seven-tenths of an inch in total length, 

 could be seen pellmell in each pouch. The yolk bag was still to be observed in the shape of a hernia 

 under the abdomen ; the pectoral and ventral fins showing no signs of tlieir presence. The 

 spinous portion of the dorsal existing in a rudimentary state only, there being a few spines close 

 to the anterior margin of the articulated portion of the same fin, which is greatly developed, 

 as well as the caudal and anal, the anterior spines of which are not yet to be seen. The central 

 rays of the caudal are much longer than the lateral ones, giving to that fin almost a spear- 

 shaped appearance. The peduncle of the tail is very well developed ; the posterior rays of either 

 the dorsal and the anal do not extend to the base of the caudal, though proportionally more 

 developed than in the adult. The head is rounded, and the cleft of the mouth but slightly 

 indicated. The eye consists of an external layer of black pimentum. 



This species inhabits the Bay of San Francisco, where it appears to be common. 



Plates XXVII and XXVIII represent Emhiotoca jacksoni . 



Plate XXVII, fig. 1, is the male sex somewhat reduced in size. 



Fig. 2, a section of tlie same, across the line of greatest depth of the body. 



