CLASSIFICATION or THE TUNICATA. 579 



A [With a single gonad, placed on the rigliL side Dendrodoa. 



\ Wit h gonads ou both sides 5 



P- /Stigmata curved , Glandvila. 



\ Stigmata straight 6 



p. f Gonads few, elongated, tubular Styela, 



I Gonads numerous, small " polycarps" .... Polycarpa. 



Styeloides, Sluiter, 1885. 

 . 'Branchial sac eutirely absent. 



Tentacles simple. 



Alimentary canal absent. 



This includes a single species, Styeloides alranchiata, a remark- 

 able form found by Sluiter near the island of Billiton in the 

 Malay Archipelago. 



Pelonaia, Forles and Goodsir, 1841. 



Body cylindrical, elongated, unattached. Apertures anterior, 

 not lobed. 



Test coriaceous, wrinkled, partly iocrusted with sand. 



Branchial sac with no folds. 



This genus includes two forms which may be separate species, 

 viz. : — 



Eody much elongated ; surface rough, wrinkled, deep brown. 



P. corrugata, Forb. (N.W. Eur.) 

 Not so much elongated; surface smooth, pilose, greenish yellow. 



P. glabra, Forb. & Goods. (N.W. Eur.) 



'Ba.twiotscjj^, Herdman, 1882. 



Body ovate or discoid, sessile, attached; apertures incon- 

 spicuous. 



Test membranous and thin. 



Branchial sac with several slight folds on each side ; meshes 

 square, no stigmata nor fine longitudinal vessels. 



Dorsal lamina a plain membrane. 



Tentacles simple. 



Alimentary canal on the left side. 



Gonads a single elongated mass or several small masses 

 attached to the mantle on each side. 



This is a very remarkable and entirely deep-sea genus. It 



.contains three species, all obtained during the 'Challenger' 



Expedition, and all from very deep water, viz. 1600, 2300, and 



3125 fathoms, the latter being the greatest depth, I believe, from 



which Ascidians have ever been obtained. 



