THE ORDERS OF TELEOSTOMOUS FISHES 489' 



The order as thus constituted is trenchantly separated by the 

 loss of the mesocpracoid from the Isospondyli, with which it 

 agrees in: (i) the suspension of the shoulder girdle from the 

 skull by the posttemporal, (2) the abdominal position of the 

 pelvic fins, (3) the persistence of the pneumatic duct connecting 

 the air bladder with the gut, (4) the soft -rayed character of the 

 fins. The derivation of the group from Cretaceous Isospondyls 

 is probable. "The Esocidas" says Dr. Smith Woodward, 1 "are 

 essentially fresh- water Scopeloids, and the Cyprinodontidse 

 [Pceciliidas] are generally admitted to be closely allied to this 

 family. Nothing of importance is known concerning their 

 geological history." Jordan and Starks mention the following 

 additional characters as defining the Haplomi proper: (5) 

 alisphenoids not meeting in a median line in front of brain case, 

 (6) the supraoccipital wedges in between the parietals (a mor- 

 phological advance beyond the more primitive families of Isos- 

 pondyli), (7) the exoccipitals are separated by the basioccipital, 

 a frequent character among the lower Teleosts (Starks), (8) the 

 post-clavicle is composed of a single element, (9) actinosts four, 

 (10) opercular bones all present, (11) pectoral fins placed low, 

 (12) dorsal fin placed more or less posteriorly, (13) head usually 

 covered with cycloid scales like those on the body. 



To this assemblage Boulenger 2 adds besides the forms usually 

 called Iniomi the following families, and adopts a more elastic 

 definition of the order Haplomi. 



1. Galaxiidae or Southern Pikelets. This family and the 

 nearly related Haplochitonidse are more primitive than the true 

 Pikes (Esocidae) in that: (1) the supraoccipital has not yet 

 pushed aside the parietals to gain contact with the frontals, 

 (2) an adipose fin (in the Haplochitonidas) is present. Swinner- 

 ton 3 says of Galaxias, "In some respects, e.g., forward extension 

 of the cranial cavity, and the condition of the articular head 

 of the hyo mandibular, it is as lowly as, or even more lowly 

 than, the salmon." 



l Cat. Foss. Fishes, Brit. Mus., Part IV, 1901, p. ix. 

 2 Boulenger, G. A., Cambr. Nat. Hist., Vol. " Fishes," p. 605. 

 3 "The Osteology of Cromeria nilotica and Galaxias attenuatus^'^Zoo 1 -- 

 Jahrb., 1903, Bd. XVIII, pp. 58-70. 



