NEBELA DENTISTOMA. 121 



by the form and structure of the test as well as the 

 character of the mouth. When a test of N. dentist on i a 

 is crushed, especially if it be largely composed of lenti- 

 cular pellets, an uneven fracture is produced. The 

 fracture always follows the lines of least resistance; 

 it separates the pellets but does not break them; 

 whereas a test of N. collaris or N. tincta similarly 

 treated would merely be pressed out of shape. Tests 

 of N. dentistoma occurring in clean Sphagnum are 

 beautifully transparent. The protoplasm of the living 

 organism is colourless, except for the presence of 

 chlorophyllous food-particles. As a rule the nucleus 

 is easily distinguishable and one or more clear 

 vacuoles are usually present. 



Near Llyn Idwal, and in other parts of North Wales, 

 we have frequently met with a form which, whilst 

 presenting many of the characters of N. dentistoma, 

 is neither crenulate nor dentate, but almost smooth at 

 the mouth and on the lateral margins. The test is 

 usually smaller than that of typical dentistoma, and is 

 generally covered with diaphanous scales of irregular 

 shape. Were it not, in other respects, so close to 

 the species under consideration, it might justifiably be 

 regarded as distinct. 



[This form (PL XXVIII, figs. 12 and 13) appears at 

 least to merit varietal rank, and may be called var. 

 laecis, that name, though not in the MS. of this work, 

 being written by Mr. Cash in our Wicklow list. It 

 occurred in a small sphagnous pool on the Great Sugar 

 Loaf Mountain (the Killough locality).] 



15. Nebela vitrsea Penard. 

 (Plate XXVIII, figs. 14-17.) 



Nebela vitrsea PENARD in Eev. Suisse Zool. VII, 1 (1899), p. 

 43, t. iv, ff. 5-16; Faune Bhiz. Leman (1902), p. 372, ff. 

 1-8 ; Sarc. grands Lacs (1905), p. 40, 2 ff. (p. 41) and ? 

 in Pr. R. Soc. Edinb. XXV, 8 (1905), p. 594 ; STEINMANN 

 in Ann. Biol. Lacustre, II, 1 (1907), pp. 38, 131. 



Test about the size of the preceding and liable to 



