368 MR. J. D. MACDONALD ON THE ANATOMICAL CHARACTERS 



stomach which curves gently downwards and backwards, and gradually diminishes in size 

 to the point where it becomes continuous with the intestiae. The latter coiirses back- 

 wards and then upwards on the right side of the body, untU, having arrived opposite the 

 branchial opening, it bends suddenly forwards, forming a simple loop, and again passes 

 towards the stomach, above but parallel with its former course, to terminate in the cloacal 

 chamber close to the position of the mouth. 



The liver is of a rudimentary character in this species, consisting of minute sacculations, 

 which emboss the surface of the stomach, and impart to it a rich amljer or brown hue. 



The ovaria are two in number, one lying on either side of the body, between the 

 branchial membrane and the muscular coat. The right ovarium does not occupy the loop 

 of intestine, as it does in Boltenia and most other Tunicata, but is placed in a recess in 

 front of it. These organs are pyriform in shape and laterally compressed, with the 

 smaller end and the short duct issuing from it directed towards the cloaca. The testes 

 are also two iu number, consisting of numerous elongated and finely-divided lobules 

 radiating round the base of the ovaria. 



II. In Hamelin's Harbour, Shark Bay, a second species of this genus, but of much larger 

 size, is rather plentiful. TJnUke that just described, it appears to lie loosely, or with a 

 very slight attachment, on the sandy bottom, being too massive to be supported on the 

 delicate stem of a Zostera or an Amphibolis. 



The body of the animal is somewhat rounded, compressed on the sides, and averages 

 one inch and six-tenths in antero-posterior measurement, and one inch and three-tenths in 

 the vertical direction. 



The test itself is very thin ; but numerous branched and interlacing fibres, often tubular, 

 and containing prolongations from the mantle, arise from every part of its outer surface, 

 and form a matrix for the lodgement of shell and coral grit, foraminifera, and other extra- 

 neous matters. In this way the coat assumes a thickness of about one-fifth of an inch. 



The external openings lie nearly on the same plane upon the upper or neural surface ; 

 but they are usually so surrounded with small and irregular processes of the test, that it 

 is difiicult to determine their actual configuration ; they are, however, connected by a 

 straight fold of the test, as in the former species. 



The mantle presents an almost uniformly greenish-yeUow tint, produced by minutely- 

 divided and reticulated vessels. 



The fibres of the muscular coat are delicate, and rather loosely disposed over the general 

 surface of the body, though very strongly developed round the branchial and cloacal 

 openings, in circular and radiating bundles. The lining membrane of the latter opening 

 presents a rosy hue ; and just within the margin of that which leads to the respiratory 

 chamber spring several tentaculiform bodies, which appear to correspond with the dupli- 

 catures of the contracted aperture. The true tentacula, however, always lie internal to 

 these or their modifications in the Tunicata generally. 



The tentacula in the present, as in the former species, are compound, consisting of a 

 tapering central portion, with six or seven pairs of subramose lateral processes, openly set 

 with minute papillse. Both the axis and rami are crested or angulated in the. middle, 



