GILBERT AND STAKES — FISHES OF PANAMA BAY 



175 



The species varies greatly in depth, in squamation, and in the length of the 

 dorsal spines. The depth varies from 4| to G in length to base of caudal. The scales 

 grow larger posteriorly, and are there regularly arranged. More anteriorly, they are 

 reduced in size and crowded, and are very difficult to enumerate. Different speci- 

 mens vary greatly in size of scales, in amount of crowding and irregularity in the 

 anterior part of the body, and also in the relative completeness with which the ante- 

 rior part of the body is invested. The head, nape, and belly, and a strip along base 

 of spinous dorsal are always naked. A narrow vertical strip immediately behind 

 pectorals is usually scaleless. The scaly area of sides therefore narrows anteriorly 

 and ends at a point about opposite the first dorsal spine. In some specimens the 

 scales cease more posteriorly, ojjposite fourth or fifth dorsal spine. This condition 

 does not differ essentially from that found in Microgohius signatus, the type of the 

 genus, nor in 31. thalassiinis. The genus Zalyjmus, based on embleuiaticus, must 

 therefore be withdrawn. As above indicated, the enumeration of the rows of scales 

 is attended with great difficulty, and cannot be made with any high degree of 

 accuracy. In different specimens, our counts have varied from 45 to 70, the majority 

 ranging between 55 and 65. 



The third, fourth and fifth dorsal spines are usually somewhat produced, often 

 extending to middle of dorsal base, or even beyond this point. In some specimens, 

 apparently females, the fin is evenly rounded in outline, with none of the rays pro- 

 duced. Microgobius cijdokins was based on a specimen, 5 cm. long, from the Gulf of 

 California, said to differ from 31. einblemnticus in the lower spines, the larger scales, 

 and in the presence of a round black humeral spot. Our present material shows that 

 all of these characters fall within the range of variation of M. emblematicus, of which 

 M. cyclolepis is doubtless a synonym. 



The dentition is as follows: The upper jaw is provided with an anterior series 

 of slender canines extending along the proximal half only of each premaxillary. 

 Those nearest the center of each jaw are upright, backwardly curved toward their 

 tips; the others are strongly curved (almost hooked) in the direction of the angle of 

 the mouth. Behind the canines is a single series of minute villiform teeth, extending 

 much farther laterally than do the canines. The mandibular teeth are arranged like 

 those in the lower jaw, the outermost canine on each side larger than the others. 

 Opposite the point where the anterior series terminates, the teeth of the posterior row 

 are abruptly transformed into laterally curved canines, which i-eplace on the sides of 

 the jaw those of the anterior row. 



In ten specimens, the fin-formula is as follows, the last ray of both dorsal and 

 anal divided to the base and enumerated as one ray: 



