42 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



and six circumorbital bones are present; undoubtedly, this increase 

 has occurred by the breaking up of the percoid second suborbital into 

 two components, each with a single neuromast. Further change in 

 the system may take place in three fashions. First, disintegration may 

 come to involve the lacrimal, as apparently occurs in the zoarceoid 

 Ly codes, in which the lacrimal is divided into two almost separate 

 portions. Second, in fat-cheeked forms, the lower circumorbitals may 

 leave the orbital border, as occurs in the notothenioid CJieimarrichthys 

 (fig. 7a) and again in the zoarceoid Lycodes. Finally, the central por- 

 tion of the circumorbital system may drop out entirely, as occurs in 

 the notothenioid Bembrops or the zoarceoids Lumpenus and Ptilichthys 

 (Makushok 1961b, p. 235, fig. 4). 



In addition to the various stages and types of circumorbital dis- 

 integration occurring in the notothenioids and zoarceoids, there are 

 frequent instances of a complete reversal of the trend itself. Thus, 

 among zoarceoids, the anarhichadids have a strongly constructed, 

 nearly rigid circumorbital chain of bones (Barsukov, 1959, pis. 7-16). 

 Among the notothenioids, the circumorbital series forms a more or less 

 rigid ring of bones in Hemerocoetes and Harpagifer (fig. 76), and in 

 Crystallodytes , this ring is made up of only three bones (Gosline, 1963). 



As contrasted with the notothenioids and zoarceoids, the general 

 trend of circumorbital bones in the tropical blennies, trachinoids, and 

 congrogadoids is toward a strengthening of the ring and a consolidation 

 of its elements. Again, various processes are involved. Some of these 

 are well indicated within the single genus Trachinus. In T. draco (fig. 

 7c), which approaches the percoid condition more closely than any 

 other member of the Blennioidei, there are a lacrimal and five cir- 

 cumorbitals, with a well developed subocular shelf on the second. 

 In T. radiatus, the whole chain forms a rigidly interlocked series of 

 bones; the lacrimal and what was the first circumorbital of T. draco 

 are united rigidly; there is a subocular ledge running all the way around 

 the bottom of the orbit; and the first circumorbitals have also expanded 

 downward over the cheek, foreshadowing the condition in the "urano- 

 scopoid families." 



At the posterodorsal end of the circumorbital series, two different 

 things may happen. One appears to be a simple loss of elements. 

 Thus, in T. vipera, I can find only two circumorbital bones above 

 that which bears the subocular shelf, instead of the three of T. draco. 

 Again, among the congrogadoids, there are two circumorbital bones 

 above that bearing the subocular shelf of Congrogadus, but in the 

 related Notograptus, there is only one. 



A different development of the uppermost circumorbital bone occurs 

 in the topical blennies. In Enneapterygius and to some extent in Clinus, 



