5:96 PROF. w. A. hkrdman's revised 



Pachychl^jta, Serdman, 1880. 



Body attached, sessile. Branchial aperture 8-lobed, atrial 



6-lobed. 



Test cartilagiaoas — or tougher, like india-rubber — very thick, 



solid and opaque. 



Branchial sac longitudinally plicated. Internal longitudinal 

 bars bearing large papillse at the angles of the meshes. Stigmata 

 straight. 



Dorsal lamina in the form of a membrane. 



Tentacles simple. 



Alimentary canal large, placed on the left side of the branchial 

 sac. 



Three species are distinguished from the species of Ascidia 

 by their remarkably thick and rigid tests : — 



{Dorsal lamina not toothed at the margin. 

 P. gigantea, Herdm. (S. Atl.) 

 Dorsal lamina strongly toothed at the margin 1 



(Trans, vessels in branchial sac of two sizes, placed alternately ; papillse 

 not lobed P. obionga, Herdm. (Aiistr.) 

 Trans, vessels all one size ; papillas lobed. 

 P. ohesa, Herdm. (Austr.) 



Abtssascidi.v, Herdman, 1880. 



Body oblong, attached by ventral surface. Branchial aperture 

 with from 8 to 12 lobes, atrial with from 6 to 8 lobes. Apertures 

 far apart. 



Test soft, cartilaginous, and transparent. 



Mantle thin. Muscle-bands chiefly on one side, irregular and 

 feeble. 



Branchial sac very delicate, not longitudinally plicated. Slig- 

 niata straight. 



type specimens of some of Alder and Hancock's species which are in his col- 

 lection, and I hope in time to be able to examine the rest, and perhaps to re- 

 establish or clear up the synonymy of some of the little-known or doubtful 

 forms. Dr. Norman has drawn up for me the following paragraph explanatory 

 of the very meagre published descriptions of the species named by these excellent 

 investigators : — 



" It is much to be regretted that an important work on British Tunicata by 

 Messrs. Alder and Hancock, to the preparation of which many years had been 

 devoted, and which at the time of their death was nearly ready for publication, 

 has never been printed. No doubt in some i-espects the anatomical and phy- 

 siological results may have been partially at any rate anticipated, bnt Albany 

 Hancock's researches were always so thorough that it cannot be doubted that 

 they would disclose much of great value, while more detailed specific descriptions 

 of the species briefly described by tlie«e authors are absolutely necessary for their 

 positive identification." 



