REPORT ON THE TUNICATA. 291 



Morckellioides alderi, n. sp. (PI. VI, figs. 1-4). 



External Appearance. The colony is elongated, and is 

 rudely cylindrical in shape. It is attached by the lower part, 

 and the upper end is rounded. The colour is a light semi- 

 transparent grey, sometimes tinged with yellow or pink. 

 The surface is smooth and glistening. The length of the 

 colony is about 1*5 cm., and the greatest breadth about 1 cm. 



The Ascidiozooids are conspicuous externally. They are 

 elongated antero-posteriorly, and are not distinctly divided 

 into regions. They are closely placed, and there is no 

 apparent arrangement in systems. 



The Test is soft and gelatinous. It is of a light grey 

 colour, and is transparent. The small test cells are very 

 abundant, and present the usual variety in shape. 



The Mantle is delicate. The chief muscle bands run 

 longitudinally ; they are very distinctly seen on the post- 

 abdomen. The branchial aperture is eight-lobed, and there 

 is a long atrial languet. 



The Branchial Sac is very long. The transverse vessels 

 are numerous, and all of the same size. The stigmata are 

 of moderate size, and are arranged with great regularity. 



The Alimentary Canal forms rather a short loop. The 

 stomach is large, and its wall is areolated. 



This new species is formed for some small colonies (see 

 PI. VI, figs. 1, 2) of a clear transparent, or in some cases, 

 slightly yellowish Compound Ascidian, which were found 

 in some of the deeper shore pools near Port Erin, and 

 which, on examination, turned out to belong to the genus 

 Morchellioides. This group was formed * for some of the 

 new ** Challenger " species, and it is characterised by having 

 an eight-lobed branchial aperture, and an areolated stomach, 

 while the post-abdomen is not pedunculated. These charac- 

 ters are all found in the present species (see PI. VI, fig. 3), 

 * Report on " Challenger" Tanicata, part ii, p. 176, 1886. 



