222 DR W. A. HERDMAN ON 



contain each four to six stigmata. The horizontal membranes are slight ; there 

 are none between the smaller papillae. 



The dorsal lamina is slightly ribbed transversely, and has small denticula- 

 tions on the free margin. 



The tentacles are numerous, and so closely placed that their bases touch. 

 There are 30 or 32 large, with about the same number of intermediate smaller 

 ones. 



The dorsal tubercle is small and simple, ovate in outline, and with the 

 narrower end anterior. The aperture is anterior, with the right horn rather 

 longer than the left, but neither of them curved. No peritubereular area is 

 present. 



Locality. — Two specimens, one large and one small, were obtained, during 

 the second cruise of the " Porcupine," at Station 33, 20th July 1869, lat. 50° 

 38' N., long. 9° 27' W.; depth, 75 fathoms; bot. temp., 9°*8 C. 



These specimens are exceedingly like the common Ascidia plebeia, Alder, but 

 differ from it in some details. They have no trace of the greenish tinge so 

 characteristic of Ascidia plebeia even after preservation in alcohol, and the test 

 is firmer and stiffer. The general shape, however, and the positions of the aper- 

 tures (see PI. XXXV. fig. 1) recall the characters of Ascidia plebeia. The 

 measurements in the above description are those of the larger specimen ; 

 the smaller one is 2*6 cm. in length and 14 cm. in breadth. In the smaller 

 specimen the atrial aperture is not distant from the branchial, and is turned 

 forwards. 



The body, when the test is removed, is long and narrow, and the branchial 

 sac extends slightly beyond the viscera posteriorly (see PI. XXXV. fig. 2). The 

 stomach is large and the intestine rather wide. It is covered with renal vesicles 

 and the reproductive creca. The ovary forms thick swollen masses, and the 

 spermary small dendritic tubules scattered chiefly over the anterior part of the 

 intestine. The oviduct and the vas deferens are both greatly distended in 

 the larger specimen, and form conspicuous curved tubes on the left side of 

 the body (see PI. XXXV. fig. 2). Large quantities of ova were found in 

 the peribranchial chamber. 



The branchial sac resembles that of Ascidia plebeia in every particular.* 

 The primary papilla? are large (PI. XXXV. fig. 3), and in some cases bear 

 pinnaB or small tubercles on the sides. Smaller transverse vessels connecting 

 the intermediate or secondary papilla? appear never to be present. 



The tentacles are numerous and closely placed, more closely than I have 

 found before in Ascidia plebeia, and I can only distinguish two sizes, with an 

 occasional very much smaller one here and there. The dorsal lamina is very 

 slightly ridged and denticulated. The prebranchial zone is papillated all over, 



* Compare description in Journ. Linn. Soc. ZooL, vol. xv. No. 85, p. 288. 



