72 



WALTER GARSTANG, M.A. 



each side ; also forming a weak sphincter round each aperture ; 

 longitudinal fibres almost as well developed as the transverse, extending 

 from the oral sphincter as far as the level of the first interserial bar 

 of the branchial sac ; several longitudinal fibres arising anteriorly 

 between the oral aperture and the anterior end of the endostyle, 

 extending with the longitudinal fibres of the oral sphincter to the 

 same distance ; longitudinal fibres of the cloacal sphincter short. 



Habits. — Attached to stones or algae in shallow water. 



At Plymouth Perophora Listeri has been dredged in the estuary of 

 the Yealm, and in 4 to 5 fathoms water off the Duke Rock. Mr. Heape 

 recorded it as abundant on the rocks below the Hoe. 



There can be very little doubt that the name given by Wiegmann 

 to Lister's Perophora has been also applied to forms specifically distinct 

 from it. Lister, in his admirable paper, remarks upon the existence 

 of " finger-like processes, about eight in a row, that project nearly at 

 right angles into the central cavity " [of the branchial sac], and these 

 are shown in some of his figures. 



Giard also mentions these papillae and compares them with the 

 papillse which were figured by Savigny in his account of Diazona 

 violacea. These papillse are simple and digitiform, so that Giard's 

 species probably did not differ from Lister's with respect to these 

 structures. 



On the other hand the species found at Naples and, as I gather 

 from Professor Herdman's paper, at Banyuls also (by Lahille) 

 present considerable differences from this simple arrangement. It is 

 probable, therefore, that Perophora Listeri does not occur in the 

 Mediterranean but is confined to the Atlantic shores of Northern 

 Europe. 



The condition of the papillse in Plymouth specimens i3 shown on 

 Plate II, fig. 6, in a drawing taken from preserved material. These 

 structures are seen to have a flattened triangular shape and are 

 connected at their bases by very low and rudimentary horizontal 

 membranes (cf. fig. 7). In life, these papillse assume a more extended 

 digitiform shape, as Lister long ago stated. If these papillse were to 

 be connected by internal longitudinal bars (as frequently occurs in 

 the Naples species), meshes would be formed, each containing two 

 stigmata. 



