108 Bulletin 4/, Untied States National Aluseum. 



counected by a sort of glottis with the oesophagus. Tail heterocercal. 

 Skin covered with scales, which are ganoid or cycloid. As here under- 

 stood, this group consists of the two orders Rhomboganoidea and 

 Cyclogaxoidea, the Crossopteuygii* being considered as forming a dis- 

 tinct subclass. (Ganoidei Holostei, part, Giiuther, Cat., viii, 324-325, 

 328-331.) (oAof, complete ; offrtov, bone ; also called Hyoganoidea.) 



Order K. RHOMBOGANOIDEA. 



(The Gar Pikes.) 



Parietals in contact; pterotic, basis cranii, and anterior vertebra? sim- 

 ple; symplectics present. Mandible with coronoid, angnlar, articular, 

 and dentary bones; third superior pharyngeal small, lying on fourth; 

 upper basihyal wanting ; maxillary transversely divided. A cartilaginous 

 mesocoracoid. Vertebra>i opisthoccelian, that is, connected by ball-and- 

 socket joints, the concavity in each vertebra being behind. Pectoral fins 

 with mesopterygium and 5 other basal elements. Tail heterocercal. Air 

 bladder lung-like, single, connecting with the dorsal side of the a?8opha- 

 gus. This order consists of a single family, Lepisosteid.e, (pofxSor, rhomb; 

 Ganoidea; also called Ginglymodi, j/yy^^w/zof, hinge; £i(5(jf, like, in allu- 

 sion to the hinge joints of the vertebra-.) 



Family XXXII. LEPISOSTEID^. . 

 (The Gar Pikes.) 

 Body elongate, subcylindrical, covered with hard, rhombic ganoid scales 

 or plates, which are imbricated in oblique series running downward and 

 backward. Both jaws more or less elongate, spatulate or beak-like, the 

 upper jaw projecting beyond the lower. Premaxillary forming most of 

 the margin of the upper jaw ; the maxillary transversely divided into 

 several pieces. Lower jaw composed of as many pieces as in reptiles ;■> 

 coronoid present. Both jaws with an outer series of small teeth, followed 

 by 1 (or 2) series of large teeth, besides which on the jaws, vomer, and 

 palatines are series of small, close-set, rasp-like teeth. Large teeth of the 

 jaws conical in form, pointed and striate, placed at right angles to the 

 jaw ; these large teeth rest, according to Agassiz, in a rather deep furrow, 

 protected on the outside by the raised border of the jaw, and on the 

 inside by a ridge of the same nature ; these teeth are pierced in the center 

 by a foramen, which communicates with the maxillary canal, and through 

 which the nerves and bloodvessels enter the pulp cavity of the tooth; 

 the foi'ms of tlie folded layers of dentine within the teeth are peculiar. 

 Pharyngeals with rasp-like teeth. Tongue toothless, short, broad, emar- 

 ginate, free at tip. External bones of skull very hard and rugose. Eyes 

 small. Nostrils near the end of the upper jaw. An accessory gill on the 

 inner side of the opercle. Pseudobranchia^ present. No spiracles. Gills 

 4, a slit behind the fourth. Branchiostegals 3, Gill membranes some- 

 what connected, free from the isthmus. Gill rakers very short. Air blad- 

 der cellular, lung-like, somewhat functional. Fins with fulcra ; dorsal 



* I'olypteridie; all the species belonging to the OiU World. 



