30 Messrs Forbes and Goodsir on Pelonaia. 



We have styled the genus Pelonaia, {vviXog va/w), and define 

 it as follows : — 



Test, cylindrical, unattached. 



Orifices, without rays, or two equal approximated papillose 

 eminences at the anterior extremity. 



Species 1. P. corrugata. Test, deep brown, much elongated, 

 rudely wrinkled transversely/. 



In the mud-filled cavities of old shells from deep water — 

 Anstruther. It has also been taken by Dr Johnston at Ber- 

 wick. 



Species 2. P. glabra. Test greenish-yellow, smooth, pilose, 

 not nearly so much elongated as the last. 



Dredged in seven fathoms water, in mud, Rothesay Bay. 



Anatomy of P. glabra. 



1. Muscular System. — The mantle is similar to those of the 

 other Ascldiw, possessing longitudinal ,^nd circular fibres. A 

 strong band of transverse fibres passes round the mantle, im- 

 mediately below the anal orifice, encroaching on the cavity 

 principally on that side. The chief peculiarity of the mantle 

 is its firm adhesion to the test. 



2. Digestive and Bespiratory Systems. — The respiratory 

 opening is of small size, and exhibits no folds or tentacular 

 fringes. The respiratory sac is elongated, cylindrical, con- 

 tracting rather suddenly towards one side to become continu- 

 ous with the oesophagus. On the external surface of the sac, 

 there are about thirty parallel transverse ridges, which give 

 it the appearance of a plaited frill. These plaits are less 

 apparent along the course of the branchial artery and branchial 

 vein, but midway between them on each side they are very 

 prominent, and are tied each by a minute cord to the inner 

 surface of the mantle. The internal surface of the sac exhi- 

 bits along one side the serpentine double cord which contains 

 the branchial vein ; along the other side the branchial artery; 

 and from these primary and secondary perpendicular branches 

 proceeding, as in the other Ascidiw. The transverse plaits 

 on the external surface of the sac correspond to the primary 

 or transverse branches of the vessels on the internal surface. 

 The animal was not examined when alive, but cilia without 



