622 J-iidlctin 77, United States Natiotial Museu>n. 



Order X. HAPLOMI.* 



(The Pike-like Fishes.) 



Soft-rayed fishet* with the mesocoracoid wautiug, the coracoids uor- 

 lually deveh)ped, and the post-temporal normally attached to the cra- 

 nium. Parietal hones separated hy the snpraoccipital. Symplectic pres- 

 ent. Opercular bones well developed. Anterior "vertehne unmodified. 

 Scapular arch joined to the cranium by a post-temporal. Hypocoracoid 

 and hypercoracoid separate, with developed actinosts. Pharyngeal bones 

 distinct, the superior directed forward, 3 or 4 in number, the inferior 

 not falciform. No interclavicles. Mouth with teeth. Air bladder w4th 

 a distinct duct. Ventral fins abdominal, rarely wanting; pectoral fins 

 placed low ; dorsal fin more or less posterior, the first ray occasionally 

 stiff'ened and spine-like; no adipose fin. Head usually covered with 

 cycloid scales like those on the body. Species chiefly inhabiting fresh 

 water. This order is, in some regards, intermediate between the Ixospon- 

 (hjli and the JcaniJiopteri. Part of its species, at least, are remnants of a 

 more ancient fauna than now inhabits the same waters. (u7r?6of, simple; 

 (.y/of) shoulder, in allusion to the want of the mesocoracoid, in which 

 respect these fishes resemble the more specialized spiny-rayed forms, 

 rather than the other soft-rayed fishes.) (Physostomi, part (families Eso- 

 cidcv, Umbridw, CyprinodoniUJiv, and Hetcropygii), Giinther, Cat., vi, vii.) 



a. Lateral margin of upper jaw formed by the maxillarics; preniaxillaHes not protractile; 

 vent normal. 



b. Teeth villifonn, equal; jaws not produced. Umbridjs, xc. 

 bb. Teeth cardiform, unequal; jaws depressed and produced; basis of cranium double. 



LuciiDa:, xci. 

 aa. Lateral margin of upper jaw formed by the premaxillaries; basis of cranium simple. 



c. Vent normal, abdominal; premaxillaries extremely protractile. 



PtECILIID.l:, xcil. 

 cc. Vent close behind the isthmus; premaxillaries little i)rotractile. 



Amblyopsid.'E, xoiii. 



Family XC. UMBRID^E. 



(The Mud Mixxows.) 



Body oblong, broad anteriorly, compressed behind. Head large, flat- 

 tened above. Mouth moderate, with bands of villiform or cardiform 



* In Dr. Gill's latest arrangement, the groups or orders hero called Haplomi, Synenlognalhi, and 

 Acanthopleri (exclusive of Plectotjnalhi) are united to form the order Teleocephali. As thus limited 

 the order would include those typical fislns in wliich the mesocoracoid is absent, and wliicli do 

 not show the special peculiarities of tlie !'• 'lirnhiti mid the Plcctognathi. In earlier papers of Dr. 

 Gill the ImspotiiliiJi (Malacoplen) and the Vilmiupliiisi are likewise included. The removal of the 

 Onliinophiixl is doubtless a Step in advance, but the distinctions hctvi-een tho IsospDiidi/H and the 

 Iiiiiiiiii and Utiphnui are not of the most profound character, nor are the PlectoijunOd fundamen- 

 tally ditterent from tlie Acaudiopkri. Tliere seems to us no special advantage in tlie retention of 

 a central order Tdeowphall, from which the divergent branches are separated as distinct orders. 



Wliile our knowledge of the osteology and embryology of most of the families of fishes is 

 very incomplete, it is evident that the relationships of tlie groups can not bo shown in any linear 

 series, or by any conceivable arrangement of orders and suborders. Tlie living teleost fishes 

 have sprung from many lines of descent, their relationships are extremely diverse, and their 

 differences are of every possible degree of value. The ordinary schemes have magnified the 

 value of a few common chiiracters, at the same time neglecting other differences of equal value. 

 No system of arrangement which throws these fishes into large groups can ever bo dofiuite or 

 permanent. 



