52 Scientific Proceedings, Royal Dublin Society. 



different from Ps. mixta. The species seems to be clearly distinguished from 

 Ph. pellucidus by the al3sence of deposits in the perisome, by the collar, 

 which is higher in proportion to the size of the animal, and by the very 

 differently formed deposits of the tentacles. Also the present species is 

 white, and Ph. pellucidus brown, in alcohol. 



It has been suggested that the absence of deposits in the perisome may 

 be due to age, as in C. Ryndmani (Thomps.) the deposits are frequently 

 absent in large specimens. With regard to this it may be noted that 

 Ph. pdlucidtos of 74 mm. has tables densely distributed in the perisome, 

 while Ph. Dnommondi of 70 mm. has no deposits. 



Probably Ostergren {ib., p. 21) is right in considering that Bell may have 

 had some specimens of Ps. mixta amongst his material when describing 

 Ph. Drummondi. His figure 4 (1892 a) of PL V is much more like the 

 richly perforated tables present in the perisome of Ph. pellucidtts than those 

 in the tentacles of the specimens under consideration. I have hesitated to 

 include Cucumaria communis (Forbes) in the synonymy, as his figure (1841, 

 p. 217), represents such a different-looking animal. 



Bistrihution. — Scandinavian coast, from the Sound to Lofoten. British 

 Isles (Th^el, '85), 



Pseudocucumis mixta, Ostergien. 

 ? Holothuria ncillii, Flem., 1828. 

 ? Thyonidium commune, Norman, 1869 (non Cucumaria communis Forbes ; 



nee Thyonidium commune, Diib. & Kor.). 

 ? Phyllophorus drummondii. pro parte, Bell, 1892. 

 Pseudocucumis mixta, Ostergren, 1898. 



„ cuenoti, Koeh. & Van., 1905. 



S.R. 163— Dredge, 37 fms. ? One. 



W. 210 — Dredge, 21 fms. Two and two portions. 



W. 216— Dredge, 18 fms. One. 



This species, as legards external appearance and deposits, closely 

 resembles Phyllo^ihorus ^^dhicichos (Flem.), to which species examples from 

 the two last-mentioned hauls, and two specimens in the Irish National 

 Museum from Kilkieran Bay, Co Galway, collected by A. G. More, have 

 been already referred (Nichols, 1912). Through the kindness of Mr. Nichols, 

 I was able to compare these with an example of P. pellucidus, also in the 

 Dublin Museum, taken by the E.I.A. E.xp. (Sladen, 1891). 



The following differences may be noted : — 



Ps. mixta — Posterior end of body narrow ; podia only on ambulacra ; 

 oolour in alcohol creamy white ; tentacular spicula perforated ; collar with 

 prolongations of bead-like segments. 



