82 BRITISH TUNICATA. 



below the month both the ribs and pectinations die 

 out, and the membrane becomes very narrow before it 

 reaches the bottom of the sac. The tentacular points 

 on the left side of the mouth are large and triangular 

 with the apices sharp ; sixteen or seventeen above and 

 at the side of the mouth are placed close together; 

 below, they are wide apart, usually few in number and 

 in some instances entirely wanting. The branchial 

 tubercle (PL XX, figs. 2 and 3) is oval in the antero- 

 posterior direction, with the extremities not convoluted, 

 but turned directly inwards and downwards. This 

 organ, however, appears to vary, and in two or three 

 instances it was somewhat lozenge-shaped, very large, 

 and composed of numerous irregular convolutions ; in 

 others again the loop is small and simple with the 

 extremities turned sometimes to one side, sometimes 

 to the other, and slightly convoluted. The tentacular 

 filaments at the base of the branchial tube are arranged 

 on a delicate muscular collar in a single line rather 

 close to the branchial margin; they vary in number 

 from thirty to forty-five, and are delicate, with smaller 

 ones interspersed. 



The ovary is lobulated and placed in the intestinal 

 loop, appearing at the left side. Traces of the male 

 Ceca are observed on the right side of the intestine ; 

 they are usually, however, obscured by the cellular 

 matter which thickly covers the alimentary tube, 

 particularly the stomach ; the cells are smaller than 

 usual. 



This species is closely related to A. mentida and A. 

 rulAcitndn ; the extreme hardness and thickness of the 

 test, however, and the great length of the respiratory 

 tubes, sufficiently distinguish it from both. From the 

 former it is likewise distinguished by its colour, and by 

 several other matters of detail. 



