53 319 



anterior margin embracing the origin of llie cheek-muscle; the long horizontal part 

 joins tlie quadrate in an oblicjue suture, a little past the middle of the snout; with 

 the lower part of the symplectic it connects through a rounded crest running on 

 the inner face along the upper margin. A reticulated sculpture adorns the outer 

 face of the preoperculum as well as that of the quadrate, entopterygoid and sym- 

 plectic; the more prominent crests are finely denticulated-''. 



Three opercular bones are present as usual-'. The operculum (PI. VII, 

 fig. 60) is large, somewhat fan-shaped, the surface reticulated and carrying 3 crests 

 radiating from the upper muscular process, the uppermost one following the upper 

 margin. The suboperculum (s) is a long and extremely narrow bone, almost bristle- 

 like, posteriorly tapering; keeping at some distance from the operculum it curves round 

 the anterior, lower and posterior margins of the latter. It has hitherto apparently 

 been mistaken for one of the branchiostegals. The interoperculum is disconnected 

 from the suboperculum and situated on the inner face of the preoperculum, forming 

 a very thin lamella, as usual connected by ligament with the mandible. 



Nasals and infraorbitals are completely wanting, and no lateral-line 

 canals are to be found in the preoperculum or in any other bones of the skull. 



The hyoid (PI. VI, fig. 2, 3) is very unlike that of the true Lophobranchiates, 

 being here complete, composed of all the typical parts: 2 hypohyals (hy', hy"), 

 small on the outer aspect (fig. 2), a long ceralohyal (ch), a short epihyal (eh), and a 

 very short stylohyal (st); the latter carries on its outer face a long horizontal process 

 pointing forwards and lodged into a fossa on the inner side of the preoperculum. 

 On the inner face of the hyoid (tig. 3) both hypohyals — especially the lower — 

 are produced into long processes covering the anterior part of the ceratohyal. 



The urohyal (PI. VII, fig. 3 u) is long and slender, posteriorly cleft into 2 

 long branches, the left again bifurcating. Only one branchiostegal (r) is present, 

 fixed along the outer face of the epihyal and ceratohyal. The single stem is soon 

 bent at an open angle and then divides into two slender branches, the lower of 

 which is much longer than the upper and following the equally slender suboper- 

 culum curves round the operculum about to the upper end of the gill-slit-'*. 



The branchial skeleton (PI. VI, fig. 9) is reduced and rudimentary, even 

 more than is the case in the Syngnathicke. All unpaired elements — glossohyal 

 and basibranchials (copulæ) are wanting, and there arc no traces of gill-rakers. 

 On the other hand, teeth are present on the lower and upper pharyngeals. The 

 first gill-arch consists of two slender bones about of equal length, connected through 

 an undivided cartilage; they represent the hypobranchial and ceratobranchial. The 

 second arch consists of three or four parts: a rather long hypobranchial, connected 

 by undivided cartilage with the ceratobranchial, and a very small, rudimentary 

 epibranchial, carrying a single tooth; this part may be absent; in the specimen 

 figured it is developed only on the right side ; the fourth part, the pharyngo- 

 branchial, is widely separated from the rest, united to the pharyngeal belonging to 

 the third arch. Of tlie third arch the hypobranchial is wanting, as in the Si/ngna- ^-jp' 



'à 



■v. / 



