724 SCIENTIFIC RECORD FOR 1883. 



named Gastrostomus Bairdii. It was at once evident that these fishes 

 represented a new or undifferentiated group of fishes, and which was 

 probably of ordinal value. A study of the anatomy was undertaken by 

 Messrs. Gill and Ryder, and some very remarkable structural peculiar- 

 ities were discovered. The branchial system was found to be extraordi- 

 narily reduced, and, in fact, to be less developed than in any other fish, 

 and even than in the Marsipobranchs. All the four usual branchifer- 

 ous arches, however, were present and one of those whose function is 

 diverted in ordinary fishes had resumed its branchiferous function, 

 so that five were actually present. Nevertheless the brain and heart 

 were those of Teleost fishes. Many were the other peculiarities found 

 in the new type, and those that contrasted most with the characteris- 

 tics of normal fishes or appeared to be of the highest morphological 

 value were embodied in the ordinal diagnosis, the two genera Eurypha- 

 rynx and Gastrostomus being segregated not only as a family (Eury- 

 pharyngidse) but as a distinct order, named Lyomeri. The characters 

 of these categories are as follows : 



The order Lyomeri is framed for fishes with five branchial arches (none 

 modified as branchiostegal or pharyngeal) far behind the skull; an im- 

 perfectly ossified cranium, articulating with the first vertebra by a basi- 

 occipital condyle alone; only two cephalic arches, both freely movable, 

 (1) an anterior dentigerous one, the supramaxillary,and (2) the suspen- 

 sorial, consisting of the hyomandibular and quadrate bones; without 

 palatine bones; with an imperfect scapular arch represented by a sim- 

 ple cartilaginous plate on each side, remote from the skull ; with pec- 

 toral rays spiniform and articulated directly with the scapular plates, 

 and with the dorsal and anal rays simple and not articulated. 



The family Eurypharyngids is then limited to Lyomeres, with the 

 head flat above and with a transverse rostral margin, at the outer 

 angles of which the eyes are exposed, with the jaws excessively elon- 

 gated backwards and the upper parallel and closing against each other 

 as far as the articulation of the two suspensorial bones, with minute 

 teeth on both jaws, with a short abdomen and long attenuated tail, 

 branchial apertures narrow and very far behind, dorsal and anal fins 

 continued nearly to the end of the tail, and minute pectoral fins. 



The mandibular rami are exceedingly narrow and slender, but the 

 jaws are extremely expansible and the skin is correspondingly dilatable; 

 consequently an enormous pouch may be developed. Inasmuch as the 

 slenderness and fragility of the jaws and the absence of raptorial teeth 

 (at least in Gastrostomus) preclude the idea of the species being true 

 fish of prey, it is probable that they may derive their food from the 

 water which is received into the pouch, by a process of selection of the 

 small or 1 minute organisms therein contained. 



The peculiar closure of the anterior half of the upper jaws upon each 

 other, and the coordinate joint between the hyomandibular and quad- 

 rate elements of the suspensorium are doubtless correlated with the 



