OEAL APPENDAGES IN SOME TERRESTRIAL ISOPODS. 291 



The Mandibles. — The variation (fig. 19) shows the teeth o£ the mandible 

 much more pointed than usual and a sharp curved spinous tooth arising from 

 the inside. Four cases were observed where these features were present. 

 Figure 20 shows a further modification where the inner spinous tooth has 

 come to the edge and fused, whilst the true bifid internal tooth is spinous. 



The 1st Maxillce. — The peculiar variation shown in fig. 21 of the inner lobe 

 occurred twice ; it exhibits ten spines at the distal extremity instead of the 

 tiny single spine and the two setose bristles. In a second case (fig. 22) tliere 

 were four spines at the distal extremity and five smaller ones on the inner 

 margin. A third variation observed once involved both lobes of the maxillae, 

 the outer lobe terminating distally in two large and one smaller spine, whilst 

 the inner lobe terminated in a dense brush-like mass (fig. 23). 



ihe Maxillipedes. — Two well-defined variations were met with, one (fig. 24) 

 occurring no fewer than eight times and the other (fig. 25) four times. The 

 first is remarkable for the great development of spines both in number and 

 size, whilst in the other case there is a corresponding absence. In both cases 

 the form of the outer lobe approaches that which obtains in normal examples 

 of Philoscia muscorum (Scopoli) and again in Forcellio ratlikei, Brandt, 



5. PORCBLLIO LiEViS, Latr. (PI. 21. fig. 26.) 



Thirty-six specimens were examined, but only one variation was found, 

 which occurred in the 1st maxillae. The outer lobe terminated in a large, 

 curved spine followed by three smaller ones, then there was a distinct blank 

 space bearing no spines, and below this five much finer spines were present 

 (fig. 26). The inner lobe in all five cases terminated distally in four long 

 curved spines. 



6. PoRCELLiONiDES PRUINOSUS (Brandt) Stehbing. (PI. 21. figs. 27-30.) 



Sixty-eight examples were examined of this cosmopolitan species and four 

 variations noted. Three of the specimens were from Northern India, and in 

 all of these the variation shown in fig. 2d) was present. 



The 1st Maxillce. — Two well-marked variations occurred,, one in two 

 examples (fig. 27) in the spines of the outer lobe, which terminated in a large 

 and prominent spine, with a smaller one arising from the inner side of the 

 plate of the lobe. Below the large spine were six short spines, one below the 

 other. In the second case (fig. 28) the variation was noted in three specimens 

 from Northern India and in another example from the Channel Isles. Here 

 the spines of the outer lobe were well defined, and in all cases there was the 

 smaller spine arising from the inner side of the plate of the lobe. The distal 

 extremity of the inner lobe in all four specimens terminated in a flat plate- 

 like palp (tig. 2^). 



