236 THE VOYAGE OF H.M.S. CHALLENGER. 



however, sections made in various parts show that the notochord is continuous and 

 persistent, and that the centra of the vertebrae are only very thin rings of bone. The 

 abdominal vertebrae are short, deeply pitted, sixty in number ; they are provided with 

 very short zygapophyses, feeble neural spines, and, below, with rudimentary ribs which 

 can scarcely be distinguished from fibrous ligaments. The caudal vertebrae are very 

 similar to those of the trunk, and provided with very feeble, needle-like neural and 

 haemal spines. Those constituting the extremity of the tail are very narrow and elongate, 

 and consist of a centrum only. The first interneural is a broad lamella with a pair of 

 diverging ridges, and attached to the neural spines of the thirty-first, thirty-second, and 

 thii-ty -third vertebrae. Interhaemal spines rather short and feeble. 



The scapulary arch (fig. 2) is very simple and weak. The clavicle (cl) is a narrow, 

 slightly curved, sword-shaped bone, tapering at the symphysis, and terminating in a 

 short point at its junction with the supraclavicle. It is suspended from the skull by 

 two supraclavicles, of which the upper (scl) is the shorter, and slightly dilated at its 

 distal end. The scapula (sc) and coracoid (co) form an extremely thin lamina, subcircular 

 in shape. The pectoral rays are joined to four minute basalia. A postclavicle is 

 absent. 



The pubic bones are also very weak, consisting of a thin semicartilaginous rod, dilated 

 inw\ards into a very thin and weak, bony lamella ; their base is swollen for the insertion 

 of the fin-rays and cartilaginous. 



Hcdosaurus owenii. 



Halosaurus owenii, Johns., Proc. Zool. Soc. Lond., 1863, p. 406, pi. xxxvi. fig. 2. 

 „ „ Giintli., Fish., vol. vii. p. 482. 



B. 14. D. 11. P. 11. V. 10. L. transv. 14 | 6. 



Snout produced ; its praeoral portion being nearly one half of its length. Eye rather 

 large, the length of its diameter being two-fifths of the postocular portion of the head, 

 and much more than the width of the interorbital space. The maxillary reaches the 

 vertical from the front margin of the eye. The length of the head is more than its dis- 

 tance from the ventral fin, the base of which is entirely in front of, and somewhat remote 

 from the base of the dorsal. Pectoral fin with narrow base, very long, extending nearly 

 to the root of the ventral. Scales of the lateral line scarcely larger than the others, 

 without phosphorescent organs being visible in the only specimen known. Anterior 

 portion of the dorsal fin covered with small scales ; anal fin scaleless. Brownish, silvery 

 on the abdomen ; gill-cover blackish. 



The typical specimen from Madeu'a, 17^- inches long, is still the only individual 

 kuown of this species. 



