18 OSTEOLOGY OF SCOMBROID FISHES 



The three families here considered differ but little from the family 

 Scombridas. The eye has no bony sclerotic case, there are no separate 

 bony baseosts, and the caudal rays are not deeply divided at the base 

 to receive the hypural plate. 



These three families have the following characters in common: 

 prefrontals meeting at the median line, with the ethmoid appearing 

 nowhere between them posteriorly; alisphenoids separated from each 

 other; supraoccipital .extending over the epiotic suture, but not separat- 

 ing epiotics as viewed from within the cranium; myodome and basi- 

 sphenoid present; the latter with a descending process; eye without a 

 bony sclerotic case; ascending processes of premaxillaries not devel- 

 oped ; supplementary maxillary present ; teeth in alveoli ; coracoid suture 

 ending at middle of third actinost from top; head of hyomandibular 

 divided into two parts; symplectic joined to metapterygoid by a den- 

 tate suture; three pairs of tooth-bearing pharyngeals present; the an- 

 terior basibranchial remote from the first hypobranchial ; anterior ribs 

 and epipleurals attached to vertebral centra; caudal rays, when present, 

 not deeply divided. 



The principal characters that differentiate these families is shown 

 in the following synopsis: 



GEMPYLIDAE (Promethichthijs) 



The pterotic and temporal crests coterminous against an oblique 

 ridge from the supraoccipital; myodome opening posteriorly through 

 a rather broad foramen; opisthotic on lower surface of cranium not 

 separating the exoccipital from the pterotic; suborbital ring complete 

 and with a sensory tube; pelvic bones attached between clavicles; no 

 parapophyses present, but haemal arches developed behind middle of 

 abdominal portion of vertebral column; no sharp ridge along the side 

 of vertebras; ribs anteriorly in pits on centra, posteriorly at tips of 

 abdominal ha?mal spines with their bases in contact as in the family 

 Scombridas ; body incased in two series of intermuscular rays, the upper 

 scries composed of epipleurals. 



LEPIDOPIDAE (Lepidopus) 



The temporal crest ending as in Promethichthys, but the pterotic 

 crest ending against middle of temporal crest; myodome opening pos- 

 teriorly through a very small pore; opisthotic partly on superior sur- 

 face of cranium, and separating exoccipital from pterotic for a con- 



