218 THE PLAGIOSTOMIA. 



Total length 34?, snout to tail 23j, snout to dorsal spine 14i snout to pec- 

 toral 85, snout to mouth 4|, and caudal fin 7 inches. 

 Uniform brown. 

 Japan: Alan Owston. 



ACANTHIDIUM ROSTRATUM. 



Plate 11, fig. 1-4. 



Acanthidium rostratum Garman, 1906, Bull. M. C. Z., 46, p. 206. 

 Centrophorus rostratus Recian, 1908, Ann. mag. nat. hist., scr. 8, 2, p. 52. 



Moderately robust, elongate, somewhat compressed. Head long, about 

 one fourth of the total length, depressed, width three fifths of the length, flat- 

 tened on the crown. Snout more than half as long as the entire head, sharp 

 edged as seen from the side, broad and broadly rounded at the end as seen from 

 above. Nostrils small, distant from one another three fifths of their distance 

 from the end of the snout or three sevenths of their distance from the mouth, 

 crossed by a short, angled lobe on the inner side of which lies a smaller one. Eye 

 large, length of orbit two fifths of its distance from the end of the snout. Mouth 

 wide, width nearly two fifths of the length of the snout, little arched; groove 

 moderate; folds short, upper longer. Teeth compressed !§; upper triangular, 

 eight near the middle of the mouth nearly erect, lateral teeth becoming more 

 oblique, with more of a notch on the outer edge; lower larger, oblique, with cut- 

 ting edge directed outward nearly horizontally above a deep notch on the outer 

 edge. Spiracle large, semihmate, distant its own width up and backward from 

 the orbit. Gill openings moderate, in front of the pectoral, hindmost wid- 

 est. Pectoral short, oblique subtruncate, outer angle rounded, inner blunt, not 

 produced. Spine of first dorsal behind the end of the pectoral fin, equidistant 

 from the subcaudal and the end of the snout, half the height of the fin, half ex- 

 posed; base of the dorsal without the spine equal less than three fourths of the 

 snout, less than half of the interdorsal space, or about four fifths of the length 

 of the base of the second dorsal, without its spine; fin low, the much produced 

 hind portion in hinder half of total length. Second dorsal spine above the axils 

 of the ventrals, two thirds as high as the fin, half exposed; base of fin three times 

 the space between it and the supracaudal, equal the space between ventrals and 

 subcaudal, or two sevenths of the space between ventrals and pectorals; hind 

 angle produced, reaching the caudal. Caudal of moderate depth; subcaudal 

 lobe somewhat produced, rounded below, fin narrow in front of the terminal, 



