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entopterygoid with the quadrate and symplectic; its inner surface is very concave; 

 its upper margin is arched and somewhat bent inwards; it is very firmly attached 

 to the ethmoid and vomer. 



The palatines (pa) in A. scutata are extremely short, in the other two species 

 somewhat longer, especially in A. punctulata; a small knob-like process projects 

 forwards from the anterior end over the maxilla; on the inner side it is articulated 

 with the anterior end of the vomer, posteriorly with the ento- and ectopterygoids. 



The preoperculum (/;ro) along its ascending part oveiJaps the hind margin and 

 a great part of the outer lateral face of the hyomandibular; from this it broadens 

 out on the cheek under the eye in a rounded flap (* fig. 10), which covers the 

 origin of the cheek muscle (add. mandib.). The horizontal portion broadens out 

 below and posteriorly into a thin, transparent lamella; the outer surface along the 

 canal for the lateral line bears a row of low, irregular projections or spines, which 

 together form a kind of ridge separating the thin expansion from the somewhat 

 firmer portion of the bone; at the corresponding place on the inner surface there 

 is a true, but fairly low ridge which terminates at the deep, articulating cup for 

 the stylo-hyal under the end of the hyomandibular. The anterior, evenly pointed 

 portion of the preoperculum is attached for a long distance to the lower margin 

 of the quadrate; in A. scutata it is considerably shorter than in the other two 

 species. 



The a bones of the gill-cover are present; the operculum (o) is oval with a 

 projection on its lower margin; its external surface is marked by line lines. The 

 suboperculum (s) is almost crescent-shaped, with broad "fore-horn". The intero- 

 perculum (/o) is extremely long and thin, concealed on the inner side of the preoper- 

 culum along the horizontal ridge of the latter; from this it follows the ridge on 

 the inner side of the quadrate right to its front end, where by means of a short, 

 thick ligament it becomes attached to the angular bone on the mandible. Its pos- 

 terior end, which reaches to the articulating cup for the stylohyal, is quite thread- 

 like; anteriorly the bone increases evenly in thickness. The posterior portion is 

 sometimes interrupted by a short stretch of connective tissue.^ 



The hyoid arch (figs. 15, 16) is represented by the normal number of bones; 

 it is short and extends backwards only to about the front margin of the hypo- 

 branchial of the first gill-arch. Its special character consists partly in the much 

 shortened stylohyal (st), partly and chiefly, in the greatly developed lowermost 

 hypohyal I {hy I), partly finally in a certain amount of displacement towards one 

 another of the parts composing it. Viewing the arch from the outer side (fig. 15) 

 the small, rounded stylohyal (st) is seen as if inserted in and surrounded by the 

 epi- and ceratohyal. It has a head-shaped, rounded articulating surface for the 

 above-mentioned articulating cup on the suspensorium; on the outer side it has a 

 deep groove (* fig. 15) which is completed by the other two bones, the epi- and 

 ceratohyal; this is filled by a short, thick ligament, which holds the hyoid arch 

 to the preoperculum (and symplectic). Very little of the cpihyal (eh) is seen from 



I). K. I). Videiisk Selsk. Ski- , 7, Række, nalurvidcnsk ni; iiKillieni. Aid. VI 'i. 9 



