55 321 



resembles that of Fistiilaria still more, as il divides into an ouler (anterior) larger (o), 

 and an inner (posterior) narrower branch (i). To the latter is joined the greater 

 part of the scapular arch, only the lower anterior end of the coracoid being con- 

 nected with the ouler branch; thus a large opening is surrounded by the clavicle 

 and the coracoid. In Aulostoma the corresponding opening is reduced to a mere 

 hole through the enlargement of the anterior part of the coracoid ; in the Syngna- 

 thids, on the other hand, the same space is open ventrally (only closed with 

 the dermal skeleton) because the coracoid here has not developed any anterior 

 process. 



The scapular arch (Pi. VII, figs. 4, 5), while in general shape recalling that 

 of Syngnathids, is in some respects intermediate between this and that of Aulosto- 

 mids, especially of Fisliilaria. The unossified, cartilaginous part of the arch is 

 proportionally much smaller than in Syngnathids, not very much greater than in 

 Fistularia. As in the Syngnathids tire scapula (sc) is very small, at first sight 

 appearing like a pterygial, but the scapular foramen is restricted to the scapular 

 region; this foramen is narrow, verticalh' elliptic, bounded by the scapula and 

 ])arl of the clavicle. The latter condition might be derived from that found in 

 Fistularia, if we suppose the thin cartilaginous anterior part of the scapula in the 

 latter to have been suppressed in Solenostonms. 



The coracoid (co) is the largest bone of the arch; its slender anterior branch 

 is tipped with cartilage, firmly connected with the outer branch of the clavicle; 

 its lower posterior angle is drawn out into a process (co') apparently corresponding 

 to that lettered in the same way in the other genera. The 4 pterygials (basais) (ba) 

 are rather large, resembling those in Syngnathids, being laterally compressed, in 

 their middle constricted into a narrow stalk; distally their cartilaginous ends are 

 confluent, forming one continuous semicircle, the upper part of which belongs to 

 the scapula. The outer face of this semicircular cartilage is even, but the inner 

 (medial) face (fig. 4) is provided with a number of elevations or columns between 

 which the tendons from the medial muscles to the fin rays are guided. Ligaments 

 passing from one to another of these columns, and the skin connecting with their 

 distal ends, convert the fossæ between them into regular holes for the tendons. 

 Thus, only the inner faces of the pterygials show structures (cartilaginous) com- 

 parable to the peculiar osseous excrescences occurring on both faces of the pterygials 

 in Syngnathids. Of the 4 pterygials the lowermost is by far the largest, as also is 

 the case in all the other genera"''. 



The base of each of the feebly ossified fin-rays embraces a separate small 

 nodular cartilage, which by means of a saddle-shaped face plays on the convex 

 margin of the combined pterygial (and scapular) cartilage ; quite as in Syngnathids. 

 Most of the fin-rays — some of the superior and inferior only being excepted — 

 are jointed; all are unbranched, the distal ends forming a bundle of extremely 

 fine threads. 



The ven tral s are almost vertical in position, with that face outwards which 



