MOLLUSC A. 41 



Family Salpidce. 



61. A Salpa maxima, the asexual form. A green rod 

 has been passed through the body-cavity, so as to protrude from 

 the anterior and posterior orifices. The test is double, being 

 composed of an inner and an outer layer : of which the latter is 

 semi-transparent, uniform in texture, and almost colourless: 

 the former is more opaque, of a yellowish tint, and provided 

 with numerous transverse muscular bands. The two are seen 

 to be united at one point on the right side near the posterior 

 orifice. 



Extending across the body-cavity diagonally, from right to 

 left, are the branchiae. In the left-hand lower corner is the 

 liver, close to which is a young chain of sexual salps. 



62. In this specimen the chain of sexual salps is nearly 

 mature, and will shortly separate from the animal. 



63. A chain of sexual forms of the same species. In 

 the centre are two specimens, chained together, of JSalpa 



pinnata. 



Bay of Naples, 1874. F. M. Balfour. 



Class POLYZOA. 



64. A Sea-Mat (Flustrafoliacea). 



The zooids in the living specimen are contained within the 

 ovoidal corneous cells of which the ramose and lamellar 

 ' csenaecium ' or ' polyzoarium ' is composed. These cells are 

 arranged on both sides of the frond in parallel longitudinal 

 rows ; examined with a lens, from four to eight short and blunt 

 spines are seen to surround the broad end of each cell. The 

 stone to which these fronds are attached is encrusted with these 

 cells. 



Class BRACHIOPODA. 



65. Two specimens of Lingula anatina. 



They have been attached to a sheet of mica. The valves 

 are of a horny texture, and of nearly equal size, differing in this 

 respect from the majority of the class, which have equilateral 

 but inequivalvc shells. Furthermore, the valves are not lateral, 



