no. 3647 PERCIFORM FISHES — GOSLINE 47 



thenioids, the basisphenoid, though generally present, is lacking in 

 the flat-headed Bembrops and is said to be absent (Regan, 1913, 

 p. 141) in the Hemerocoetidae. Among the tropical blennies and 

 their relatives, it is apparently always present. In the zoarceoids, 

 there is no basisphenoid. 



In the zoarceoid Bathymaster, the brain cavity is separated from 

 the posterior myodome only by membrane anteriorly (fig. 106), 

 though posteriorly there appears to be the usual horizontal prootic 

 ledge separating the two cavities. In such a fish as the parapercid 

 Prolatilus (fig. 10a), by contrast, the myodome is separated almost 

 completely from the cranial cavity by the wings of the basisphenoid 

 anteriorly and by a well-developed prootic ledge posteriorly. This 

 is the usual percoid condition. (For an account of variations of the 

 posterior myodome in scorpaeniform fishes, see Quast, 1965, pp. 574, 

 584.) 



In the basal percoids, the ascending wing of the parasphenoid is 

 low (as in fig. 4) and does not extend up to a junction with the 

 pleurosphenoid in front of the prootic. But again and again in the 

 percoid derivatives — and, for that matter, in lower teleosts (see, 

 e.g., figs, in Svetovidov, 1948) — the ascending wing of the para- 

 sphenoid becomes prolonged upward in front of the prootic to the 

 pleurosphenoid and, in extreme instances, meets a descending wing 

 of the frontal ahead of both the prootic and pleurosphenoid. Starks 

 (1923, pp. 261-263), Makushok (1958, pp. 41, 42), and Quast (1965, 

 pp. 572-574) discuss variations in this character. 



Among the Blennioidei, the parasphenoid always extends up to the 

 pleurosphenoid or frontal ahead of the prootic in the Zoarceoidae and 

 Trachinoidae; it does not do this in the Notohenioidae. In the tropical 

 blennies, it is variable (Starks, 1923, p. 263, and Springer, 1966). 

 Among congrogadoids, a long sliver of prootic extends forward to the 

 orbital border between the pleurosphenoid and parasphenoid in 

 Congrogadus, but in Notograptus the parasphenoid and pleuro- 

 sphenoid meet. 



Fin structure.- — -With a few exceptions, the differentiation between 

 spines and soft rays is not as clear in the Blennioidei as it is in most 

 percoids. On the one hand, pungent spines and their large pterygio- 

 phores tend to be reduced or lost. The tropical blennies are the only 

 group that consistently has dorsal fin spines. On the other hand, the 

 branching of the soft rays usually is reduced; where it does occur in 

 the vertical fins, the posterior half of each branch rebranches sooner 

 than the anterior half. In many blenniid genera, e.g., Medusablennius 

 (Springer, 1966), there are no branched fin rays at all. 



Paired fins and their girdles. — As noted above, the function 

 and structure of the paired fins in the Blennioidei are different from 



