THE GENUS LEBERTIA. 487 



Between seventy and eighty species with varieties have been 

 described. The species described here, in addition to the sub- 

 generic types (excluding brevipora), are those found within the 

 Britannic area. 



In dealing with the appendages of the body, it is generally 

 found convenient to designate the segments by number, the first 

 being invariably that which is articulated to the body. No 

 terminology has yet been agreed on, though Soar * and Koenike t 

 have discussed the matter. 



Lebertia tau-insignita (Lebert) Sig Thor. 

 (Sub -gen. Lebertia.) 



1879. Pachygaster tau-ivsignitus, Lebert, Bull. Soc. Vaud., xvi. 371. 

 1905. Lebertia tau-insignita (Lebert) Sig Thor, Zool. Anz., xxix. 

 52-59, figs. 18-24. 



This species, which has been redescribed by Thor, has, so far 

 as known at present, a restricted range, being only recorded 

 from the neighbourhood of Morges on the Lake of Geneva. It 

 is the type species, and its inclusion here is therefore appropriate. 

 Thor describes the body outline as resembling a long ellipse, 

 whose length may vary from O90 mm. to l - 40 mm. The 

 greatest breadth ranges from 0*80 mm. to l - 05 mm. The venter 

 is weakly arched, the dorsum more strongly so. The anterior 

 margin of the body between the antenniform bristles is rounded, 

 or blunted. In this it differs from L. fimbriata, which Thor 

 selected as type of the sub-genus to which both species belong, 

 as well as with regard to the extent to which the anterior 

 extremities of the second pair of epimera extend beyond the 

 body margin ; in the case of the present species they do not 

 extend much. The skin is smooth and very finely porose. 

 Sometimes, particularly in young specimens, the skin has an 

 extremely fine striate appearance, due to the presence of very 

 fine folds. These are in no way comparable to the coarse 

 ridging of the skin such as may be observed in the sub-genus 

 Pseudolebertia, but Thor's view is that they are provision for the 

 increase in size of the body, since they become obliterated as 

 growth proceeds. The colouring is unusual ; it is almost entirely 

 blackish, with a semi-transparent yellowish zone round the edge 



* Trans. Edin. Field Nat., v. 375. 

 f Ahh. Nat. ver. Bremen, xx. 158. 



