70 Mr. C. T. Regan on the Anatomy and 



not really indicate relationship to the Scombridse is shown 

 by the fact that Thyrsites has the hypural exposed to the 

 same extent as in most Perches, but is otherwise so similar 

 to Scomber in its anatomy as to leave little doubt that the 

 two genera are closely related. 



Recently, in the Introduction to the " Pisces " volume of 

 the * Biologia Centrali-Americana,' I instanced three appa- 

 rently natural groups, each of which included forms with the 

 pelvic bones firmly attached to the cleithra and others with 

 the pelvic bones remote from them ; to these the Scombroids 

 may now be added. 



Order PERCOMORPHI. 

 Suborder Scombroidei. 



Air-bladder without open duct. !Maxillaries more or less 

 firmly attached to the non-protractile prEemaxillaries, which 

 are typically produced and pointed anteriorly *. Cranium 

 with the orbito-rostral portion elongate and the postorbital 

 portion abbreviate ; parietals separated by the supra- 

 occipital ; no orbitosphenoid ; basisphenoid present ; pro- 

 otics giving rise to au osseous roof for the rayodome. 

 Vertebral column of solid centra which are co-ossilied with 

 the arches. Pectoral arch attached to the cranium by a 

 forked post-temporal ; no mesocoracoid ; pterygials more or 

 less regularly hourglass-shaped, 4 in number, 3 of them 

 attached to the scapula. Pelvic fins of a spine and 5 soft 

 rays or variously reduced, thoracic or subthoracic in position, 

 the pelvic bones attached to the clavicles. 



Division I. Trichiuriformes. 



Caudal fin-rays not deeply forked at the base, the hypural 

 in great part exposed. Praemaxillaries beak-like, free from 

 the nasals; mouth toothed, with lateral cleft; strong 

 anterior canines. Epiotics separated by the supraoccipital. 

 Gill-membranes free from the isthmus. Pectoral fins 

 placed low. 



Family 1. Gempylidae. 



Body oblong or elongate, compressed ; maxillary exposed; 

 spinous dorsal longer than the soft ; anal with 3 spines, 



* The very aberrant and highly specialized Luiarus is the onlv 

 exception. 



