268 PLEUROBRANCHIDJE. 



their interstices a red-brown colour meanders in various 

 breadths and irregular blotches, interspersed with cloudings 

 of pale yellow flakes. The body within, and the internal 

 area of the disks, are pale bluish- white, the ventral margins 

 being aspersed to an inch in depth with yellowish- white spots, 

 but the dorsal ones are plain. The head is a thick muzzle 

 springing from the centre of a slightly auricled membrane, 

 pale blue on the under surface, and on the upper sprinkled 

 with flake-white and red points ; under this membrane is the 

 mouth, within which is a spinous lingual riband that reaches 

 to the first stomach ; from its upper part spring two cloven, 

 though apparently tubular, short tentacula, united at their 

 origins but diverging to their points, marked with close-set 

 lines and snow-white dots ; the eyes are immersed in the 

 centre of the bases of the tentacula, which give them an obso- 

 lete appearance. 



This animal is an hermaphrodite Avith congression; the 

 male organs are white, placed between the disks, close to the 

 right side of the head, and composed of two processes; the 

 first is a moderately-sized, rounded, arcuated, conically pointed 

 stylet, connected with a tubular cylindrical body reflexed at 

 the margin; the second is a perfectly white thread-like fila- 

 ment issuing therefrom : these appear to be the virile appen- 

 dages; they are in continual motion, and perhaps act in 

 concert, the one being the verge, the other an epididymis or 

 spermatic cord : above them is the vulva combined with the 

 oviduct ; it is a long, conical, very white, tumid process, | an 

 inch long, with a considerable orifice. Next to these on the 

 same side, between the disks, extending nearly their entire 

 length, is the splendid branchial plume, which in the animal 

 observed measured nearly 2 inches in length, composed 

 of two gently arcuated leaves, tapering from their bases to a 

 pointed extremity; each leaf consists of about twenty-five 

 linear vessels or processes, resembling a twisted cord with 

 a longitudinal depression in its centre, which is the bran- 

 chial artery, and crossed on each side by transverse lines; 

 these cord-like fillets are closely packed together and taper to 



