444 [June 26, 



They extend anteriorly to the nasal cartilages, completely sur- 

 rounding this portion of the cephalothorax : the distal margins 

 exceed those of the ventral fins. The component digits are 47 on 

 each side. They increase in length and breadth as they recede 

 from the head, the terminal ray being the largest of the series. 

 In the recent rays the pectoral digits number from 80 to 100, and 

 in the torpedos nearly 60. 



The arrangement of the fin rays in Cyclohatis resembles that of 

 the recent rays, radiating in regular gradation from the centre to 

 the extremities, but the smaller number of the digits causes their 

 divergence to be greater, and the interspaces consequently of 

 larger extent. The actinated appearance of these organs is due 

 to this peculiarity, which has suggested the title of oligodactylus 

 for the species. The form of the phalanges is intermediate between 

 that of the rays and that of the torpedos, combining a greater length 

 and denser structure than we find in the latter, with breadth and 

 thickness exceeding the comparative dimensions of these parts in 

 the former. The digital articulations are more distant and fewer 

 in number than in the recent genera. The fork occurs at the 

 sixth articulation, — in the recent genera not before the tenth. The 

 phalangeal ossicles do not contract in diameter between the articu- 

 lations ; they have a projecting longitudinal midrib, from whence 

 they slope off to the margin, so that a transverse section would 

 show a lozenge- shaped outline. The coarse granulated structure 

 of these bones is distinctly traceable, causing a jointed appearance 

 between the articulations. The abdominal cavity, or that portion 

 behind the thoracic girdle, is nearly as large as the anterior or 

 cephalothoracic, and in this respect differs most remarkably from 

 the torpedos, where the anterior area is at least twice as large as 

 the 'posterior. In form it is slightly oval ; the pelvic arch differs 

 from that of all the recent rays I have had opportunities of con- 

 sulting, in the ^development of two elongated styloid processes, 

 from the horns of the transverse pubic cartilage, and extending 

 forwards over two thirds of the abdominal cavity. This structure 

 recalls vividly the marsupial bones of the Australian mammals. 

 The transverse cartilage of the pelvis sends out two broad processes, 

 extending backwards for the attachment of the ventral fins. The 

 proximal digit on either side is unusually large ; it extends laterally 

 at right angles to the spinal column, and at the first articulation 

 foi'ms a second right angle ; the remaining phalanges being directed 

 backwards, parallel to the spinal column. This digit is detached 

 from the remainder of the ventral fin, and is inserted considerably 

 nearer the transverse cartilage. The other fin rays are six in 

 number on each side : the first is considerably smaller than the 

 succeeding five, and curves outwards. The remainder agree in 

 character with the pectoral digits. The tarsal bones which sup- 

 port the ventral rays, are considerably smaller than in the recent 

 Skaits, in accordance with the smaller number of these bones, 

 which in the latter species range from fifteen to twenty. The 

 impressions of the claspers show these organs to have been compa- 



