30 DEEP SEA FISHES. 



bulbus. Figure 3 exhibits the internal arrangement of the intestine. The 

 number of circuits in the spiral is small, only four or five, and a diagram- 

 matic representation would somewhat resemble that of Chimaera monstrosa 

 as given by T. J. Parker, 1879, in the Transactions of the Zoological Society 

 of London, XI., PI. II., fig. 6. The peculiar structural arrangement of 

 the papillose ridges of the absorbing surfaces of the membranes within the 

 intestine of Centrosc^Uium nigrum is to be seen on Plate V., fig. 3 of the 

 present work. The caacal appendage of the intestine is elongate and 

 subcylindrical. 



On the skin the scales are more or less distant from one another ; they 

 are small harsh tubercular spines, each of which has an erect or hooked 

 slender grooved cusp, and a comparatively broad stellate base, Plate IV., 

 fig. 7. The lateral system is rather simple ; the arrangement of the canals 

 on the head does not differ greatly from that of Ism-us pundatus (Garman, 

 1888, Bull. Mus. Comp. Zool., XVII., Lat. Syst, Plate I.) or from that of 

 Isistiiis brasiliensis, Plate LXIX,. fig. 2 of the present work, except perhaps 

 in that the halves of the aural canal do not meet in the middle. This 

 separation of the part of a cannl on one side from the part on the other 

 side of the head is noted in widely different genera, for instance on Hepta- 

 branchias maculatus, Lat. Syst., PI. XIV., fig. 2, or particular canals on one 

 or on both sides of the head may be similarly interrupted, as on Somniosns 

 cardiarias, Lat. Syst., PI. XX., fig. 1, where cranials, orbitals, and occipitals 

 are disunited. What credit for such breaks in canals ordinarily continu- 

 ous may be given to individual variation is only to be determined by 

 examination of a number of specimens of whatever species may be under 

 consideration. 



The fins are of medium size ; the amount of fin area is much the same 

 in dorsals, pectorals, and ventrals. The first dorsal originates very little 

 backward of a vertical from the axil of the pectoral; the spine is triangular 

 in cross section, concave or grooved on each side, and is shorter and more 

 erect than that of the second dorsal. The origin of the second dorsal is 

 little, if any, backward of the middle of the bases of the ventrals ; the spine 

 is about one and one-half times as long as the anterior spine, and is similar 

 in structure but more hooked. On the tail the upper lobe of the caudal 

 is separated from the lower by a distinct notch and is subtruncate on the 

 hind margin ; the lower lobe is the deeper, and has its lower angle slightly 



