2892 Bulletin ^7, United States National Museum. 



Hypleural. The modified last vertebra supporting the caudal fin. 

 Hypobranchials. Bones of the branchial arches below the ceratobranchials. 

 Hypocoracoid. The lower of the 2 bones attached to the clavicle behind. 

 Hypohyals. Small bones, usually 4, by which the respective sides of the 



hyoid apparatus are joined. 



Imbricate. Overlapping, like shingles on a roof. 

 Imperforate. Not pierced through. 

 Inarticulate. Not jointed. 

 Incisors. The front or cutting teeth. 



Inferior pharyngeals. Synonymous with pharyngeals, q. v. 

 Infraoral. Below the mouth. 



Interhcemal spines. Elements supporting the anal fin. 

 Interhatmals. Bones to which anal rays are attached, in fishes. 

 Interhyal. Upper hyoid bone attached to hyomandibular. 

 Intermusculars. Synonym of epipleurals, q. v. 

 Interneural spines. Elements supporting the dorsal fins. 

 Interspinous bones. The interneurals and the interluemals. 

 Intermaxillaries. The premaxillaries ; the bones forming the middle of the 



front part of the upper jaw, in fishes. 



Interneurals. Bones to which dorsal rays are attached, in fishes. 

 Interopercle. Membrane bone between the preopercle and the branchios- 



tegals. 



Interorbital. Space between the eyes. 

 Interspinals. Bones to which fin rays are attached (in fishes) ; inserted 



between neural spines above anjj hreinal spines below. 

 Isocercal (tail). Last vertebrre progressively smaller and ending in median 



line of caudal fin, as in the codfish. 

 Jugular. Pertaining to the lower throat; said of the ventral fins, when 



placed in advance of the attachment of the pectorals. 

 Keeled. Having a ridge along the middle line. 

 Lacustrine. Living in lakes. 



Lamellce. Plate-like processes like those inside the bill of a duck. 

 Larva. An immature form, which must undergo change of appearance 



before becoming adult. 

 Lateral. To or toward the side. 

 Lateral line. A series of muciferous tubes forming a raised line along the 



sides of a fish. 



Lateral processes. Synonym of parapophyses, q. v. 

 Laterally. Sidewise. 



Lunate. Form of the new moon ; having a broad and rather shallow fork. 

 Mandible. Under jaw. 

 Maxilla, or maxillary. Upper jaw. 

 Maxillaries. Outermost or hindmost bones of the upper jaw, in iishes; 



they are joined to the premaxillaries in front, and usually extend 



farther back than the latter. 

 Mesethmoid. Synonym of ethmoid, q. v. 

 Mesopterygoid. A bone of the suspensorium. 

 Metapterygoid. A bone of the suspensorium, or chain supporting the lower 



jaw. 



Molars. The grinding teeth; posterior teeth in the jaw. 

 Muciferous. Producing or containing mucus. 

 Myocomma. A muscular band. 

 Myodome. Cavity under the brain cavity for the reception of the rectus 



muscles of the eye. 



Nape. Upper part of neck, next to the occiput. 

 Nares. Nostrils, anterior and posterior. 

 Nasal. Pertaining to the nostrils. 

 Nasal plaie. Plate in which the nostrils are inserted. 

 Neural arch. An opening through the base of the neural spine for the 



passage of the spinal cord. 



