278 12 



branchial; the second arch has all four parts developed, but the short and slender 

 epibranchial (e") is widely separated from its ceratobranchial (c); it abuts against 

 the hinder end of the flat pharyngobranchial (ph"); the latter is on the pharyngial 

 face beset with teeth, and reaches to the epibranchial of the first arch. 



The third arch also has four parts; the hypobranchial (hy"') has only a short 

 cartilaginous part lying at the same level as that of the second arch, but a long, 

 osseous process runs downwards, together with its fellow from the other side em- 

 bracing the branchial artery; the epibranchial is still weaker than that of the pre- 

 ceding arch, almost rudimentary, and still farther away from the upper end of its 

 ceratobranchial; its distal end articulates with both the third and fourth pharyngo- 

 branchial; the flat pharyngobranchial III is produced in front along that of the 

 second arch; its under face carries an ovoid patch of teeth. The fourth arch 

 consists only of two parts, the hypobranchial and epibranchial being absent; 

 the pharyngobranchial IV is shorter than the preceding but like this provided 

 with teeth. The fifth arch, as usually only one piece, carries the lower pharyngeal 

 teeth, and on the anterior or outer border some tooth-plates along the hindmost 

 gill-slit. 



At the upper ends of all the ceratohyals the branchial lamellæ (PI. II, fig. 4) are 

 continued a short way upon the pharyngeal wall, supported by semicartilaginous 

 strips of tissue, which appear as prolongations of the cartilage enclosed by the 

 osseous sheaths of the ceratohyals. 



Thus the branchial apparatus of Aulostoma foreshadows the condition found 

 in the Lophobranchii as to the skeletal parts, in the fact, that the epibranchials 

 II and III are reduced and separated from the rest of the arches, while the epi- 

 branchial IV is absent, and the basibranchials are reduced. 



The shoulder-girdle (PI. Ill, figs. 4, 5) has been so fully dealt with by Starks 

 (55 p. 629) that only some features have to be repeated here and a few new facts to be 

 pointed out. The clavicular arch is composed of but two parts, the posttemporal 

 and the clavicle, the supraclavicle being absent. The posttemporal is through 

 ligament fastened to the somewhat serrated hind part of the pterotic (not also to 

 the epiotic); its outer face lies in the skin and is sculptured; from the inner face, 

 near the ventral margin, originates a flat branch, connected through ligament with 

 the first vertebra; the posterior angle of the posttemporal further is bound by 

 ligament to a blunt process on the transverse process of the second vertebra, 

 and at the same time with the upper end of the clavicle. As is the case with all 

 the members of the group treated here, the clavicle (cl) has a superficial sculptured 

 plate, seen in the skin (PI. Ill, fig. 4) and covering part of the fin-muscles. As in 

 Fistidaria the clavicle divides distally into two branches, the inner of which is 

 united with the outer face of the scapular arch (PI. Ill, fig. 4 i); but as the coracoid 

 is produced forwards to unite also with the outer (or anterior) branch, the aperture 

 between the branches, which is large in Fistidaria (PI. Ill, figs. 8, 9), in Aulostoma 

 is reduced to a small foramen (PI. Ill, fig. 5 f) (not visible from the outer aspect). 



