42 Scientific Proceedings, Royal Dublin Society. 



Mesothuria intestinalis ( Asc. & Eath.). 



Holotlmria intestinalis, Asc. & Eath., 1767. 

 Thyonidiwii scahrum, Sars, 1868. 



S.R. 222— Trawl, 293 fms. One. 

 S.E. 327— Trawl, 550 fms. Sixteen. 

 S.E. 493— Trawl, 533-570 fms. Two. 

 S.E. 1690— Trawl, 584 fms. One. 



Previous Irish records. — Off S.-W. Ireland, 345-750 fms. (Sladen, 1891) ; 

 off Eagle Island, Go. Mayo, 70 fms. ; and off S.-W. Ireland, 190 fms. (Kemp, 

 1905). 



Many writers hold the view that M. Verrilli (Theel) is a variety of the 

 present species frequenting very deep water. E. Perrier (1902, pp. 309-12) 

 and Ostergren (1902, pp. 6-7) have shown that they are distinct. The deposits 

 in the perisome of both species are very much alike, and both may be found 

 in the same area, and here the similarity, other than generic, seems to end. 

 Specimens from our hauls, in alcohol, are absolutely unlike each other in 

 appearance. M. intestinalis is invariably of a uniform cylindrical shape, so 

 that if the tentacles are withdrawn it is difficult to recognize at which end 

 the head is situated. The body is pale brown (exceptionally almost white), 

 with a much-wrinkled surface, usually coated with debris (such as sponge 

 spicula and echinoderm spines), and the pedicels are distributed on the 

 anterior trivium as elsewhere. M. Verrilli, on the contrary, has hardly any 

 pedicels on the anterior part of the trivium, which is somewhat flat, and the 

 pedicels everywhere are much finer. In a specimen measuring 300 mm. in 

 length and 80 mm. an diameter the pedicels are usually only about half 

 the thickness of those in an example of M. intestinalis measuring 90 mm. in 

 length. As Perrier {op. cit., p. 310) has remarked, the pedicels, instead of 

 containing tables of similar size to those of the perisome, as in 31. intestinalis, 

 are too small to contain other than minute, somewhat rudimentary tables, the 

 terminal plate being also much smaller, and with more jagged edges. The 

 species is further characterized by the clean surface and white colour of the 

 body, which is usually much broader in the centre and constricted at the 

 extremities, and the latter are frequently directed ventralwards. 



Although the two species were not taken together in our hauls, there is 

 evidence to show that both occur off south-west Kerry from about 50° to 52° 

 N. lat. and 11° to 12° W. long. M. Verrilli was only taken between the 

 500 and 1000-fm. line. There are 4 records of M. intestinalis within this 

 area, against 5 records at about the 200-fm. line. Further north 



