REPORT ON THE TUNICATA OP PLYMOUTH. 73 



The opening of the duct of the hypoganglionic gland (fig. 7, c. v.) 

 is simply circular. It is situated in front of a raised triangular area, 

 whose apex is posterior ; this constitutes what is undoubtedly the 

 homologue of the epipharyngeal groove. A precisely similar structure 

 has been figured by Roule for Rhopalcea nepolitana,* and observed 

 in Sluiteria rubricollis by E. van Beneden.f From the posterior 

 apex of this area arises the dorsal lamina (fig. 7, d. I.) as a low 

 membrane which increases slightly in height as it extends posteriorly 

 At the level of each horizontal membrane it rises up into a curved 

 triangular languette (I), and occasionally there is a small projection 

 from its edge between each pair of interserial languettes (fig. 8, i. p.). 

 An examination of fig. 7 also shows that the horizontal membranes 

 really are continued upon the lateral faces of the dorsal lamina, although 

 they do not extend along the languettes. 



The structure of the dorsal lamina in this species approaches 

 closely in essential features that described by van Beneden in Sluiteria 

 rubricollis, in which form there is a continuous longitudinal membrane 

 whose border is cut into festoons in correspondence with the number 

 of transverse (interserial) bars. The lamina is provided with fourteen 

 oblique ridges which also correspond in number with the horizontal 

 bars. Although in his diagnosis of the genus Sluiteria, Professor van 

 Beneden denies the presence of horizontal membranes (I. a, p. 43), he 

 admits in his description of S. rubricollis that the connecting ducts of 

 the internal longitudinal bars " spring by an enlarged base from little 

 interserial folds traversing the length of the transverse bars " (p. 34). 

 This is precisely the condition I have found in the Naples Perophora, 

 and it is essentially similar to what is here described for P. Listeri ; 

 interserial membranes are in each case present, but rudimentary. The 

 ridges on the lamina of S. rubricollis are therefore undoubtedly of the 

 same nature as the less conspicuous elevations formed in P. Listeri by 

 the continuation of the horizontal membranes upon the sides of the 

 lamina (see fig. 7). Further the lamina of Slueteria rubricollis is 

 described as being enrolled, the concavity being to the right ; my 

 figure also shows that the marginal languettes of P. Listeri are bent 

 over in a precisely similar way. 



* Roule, Rev. des Esp, de Phallusiade'es de Provence, Rec. Zool. Suisse, iii, 

 pL xiv, fig. 14. 



fEd. van Beneden, Sur les genres Ecteinascidia, &c, 1. c, p. 35. 



