Beaumont — Fauna and Flora of Valencia Harbour, Ireland. 825 



species from its allies, apart from the pigment bands on the 

 head ; and examples intermediate in pigmentation are not 

 infrequently met with, as already noticed. The more oval shape 

 of the head is not a constant feature, and the median white 

 dorsal line, considered by Jonbin its most reliable character, is 

 frequently absent in specimens having the two pigment bands 

 of T. vermiadatum, and, on the other hand, is often present in 

 allied species. 



Examples of both sexes, from 1 cm. to 2 cm. in length, were 

 noticed, with well-developed gonads. 

 Testrastemma cephalophorura (?) Biirger. 



Tetrastemma cephalopliorum, Biirger (1895, p. 583) 

 Prosorhochmus Claparedi, Riches (1893, p. 20); Beaumont (1895, 

 p. 369). 



The Nemertine here, with some hesitation, referred to the 

 Tetrastemma cephalophorum of Biirger, is identical with that de- 

 scribed from Plymouth by Riches (1893),^ and by myself from 

 Port Erin (1895) as Prosorhochmus Claparedi. 



I now believe the determination of this form as Prosorhochmus 

 to have been an error. In the absence of any really useful 

 characters in the diagnoses of the genus at that time available, 

 I was chiefly influenced by the very characteristic form of the 

 central stylet apparatus, which bore a marked resemblance to 

 M'Intosh's figure of that structui'e in P. Claparedi. The possi- 

 bility of our animal being a distinct species was pointed out, 

 our specimens when well extended presenting little resemblance 

 to the figures of P. Claparedi \ but the remarkable shape of the 

 head in the latter, was sometimes assumed by individuals when 

 contracted, and the possibility of the drawings having been 

 made from contracted specimens was recognised. 



In Biirger's classification (1895), Prosorhochmus is removed 

 from the family Tetrastemmidse, and appears as the type of a new 

 family, the Prosorhochmidse, whose members are characterised 

 by attaining a great length (compared with Tetrastemmidse) ; 

 by the arrangement of their four eyes in a rectangle with long 

 axis transverse; by the small, almost rudimentary, cerebral 



1 1 have also found the species under consideration during the past two years at 

 Plymouth ; and having heen able recently to submit living specimens to Mr. Riches, 

 all doubt concerning the identity of his species, and that met with by myself, has 

 been set at rest. « 



