PHYSOCLISTL 37 



593. TV. avocetta Jordan & Gilbert. 



Head slenderer, its depth one-ninth its greatest length. Eye large, 

 one-third the head, without snout. Length of pectoral scarcely greater 

 than height of anal, which is scarcely less than the greatest depth of 

 the body, and more than the greatest depth of the head. Translucent; 

 belly with close-set dark spots, its lower edge and anal fin black, the 

 back abruptly white and unspotted. L. 22 inches. Head 10; depth 58; 

 depth of anal 64 in length of body. Puget's Sound; one example 

 known, differing in some slight respects from all Atlantic specimens 

 examined. 

 (Jordan & Gilbert, Proc. U. S. Nat. Mus. 1880,409.) 



SOB-CLASS PHYSOCLISTL 



(The Physoclistous Fishes.) 



Air-bladder, if present, without pneumatic duct, in the adult. Parietal 

 bones separated by the supraoccipital. Ventral fins usually thoracic or 

 jugular, normally with 1 spine and 5 soft rays. Pectoral fin normally 

 inserted high, with vertical base. Vertical fins usually with spines. 

 Premaxillaries normally forming the entire border of the upper jaw. 

 Tail homocercal. (<pu<r6z, bladder; xAstVru?, closed.) 



ANALYSIS OF THE ORDER OF PHYSOCLISTI. 



a. Scapula suspended to the anterior vertebrae ; maxillary distinct ; superior bran- 

 cliihyals and pharyngeals present ; inferior pharyngeals not united; no 

 interclavicles ; body elongate ; ventral fins abdominal or wanting. 



OPISTHOMI, P. 

 aa. Scapula suspended to the cranium by a post-temporal. 



b. Lower pharyugeals co-ossified ; fins without spines ; ventral fins abdominal ; 

 third and fourth superior pharyngeals much enlarged. 



SYNENTOGNATHI, Q. 



bb. Lower pharyngeals separate (or if united, fins with spines and ventrals thoracic), 

 c. Gills tufted ; superior branchihyals and pharyugeals and basal brauchihyals 



wanting; ventrals, if present, abdominal LOPHOBRANCHII, E. 



cc. Gills pectinate. 



d. Superior branchihyals and pharyngeals reduced in number ; ventrals abdom- 

 inal HEMIBRANCHII, S. 



dd. Superior brauchihyals and phary ugeals normally developed ; ventrals mostly 



thoracic or jugular. 

 e. Bones of the jaws not united. 

 /. Pectoral fins not pediculate, the gill-openings in front of them. 



y. Cranium normal ACANTHOPTERI, T. 



gg. Cranium anteriorly twisted ; both eyes on the same side of the head. 



HETEROSOMATA, U. 



ff. Pectoral fins pediculate, their basal bones reduced in number and elon- 

 gate ; gill-openings in the axils PEDICULATI, V. 



ee. Bones of the jaws co-ossified; the deutary with the articular, andthepre- 

 maxillaries with the rnaxillaries PLECTOGNATHI, W. 



