( Ixxviii ) 



a row of toothed and notched eminences all down one side of 

 the clasp, donzellii and eros ; the other members of this little 

 set are without these. 



" The other photographs shown are not intended to enable 

 you to distinguish the several species by the appendages, but 

 rather to show how much alike these various species are, and 

 by what small differentia they may be distinguished from 

 each other. I may say, however, that there is a peculiarity 

 about both the dorsa and the clasps that increases the difficulty 

 of seizing distinctions between the different forms. The dorsal 

 armature of either side has a strong chitinous frame, but it 

 has also a soft portion that I may call a wing. This soft 

 portion may be very expanded or contracted, and as it is so, 

 gives to specimens of one species a greater variety of appear- 

 ance than really subsists between some different species. The 

 same is true of the clasp ; there is a soft median portion, 

 between the rounded and haired division of the serrated end. 

 This soft portion allows of these two ends being nearer 

 or further apart, of the turning over of the serrated end, and 

 also itself may project more or less between the two terminal 

 portions, often looking like a tliird division, even of more 

 importance than the other two. It appears to present im- 

 portant specific characters, until one learns to give it its true 

 value. 



"As distinguishing coridon from thetis the dorsal hooks 

 of coridon have a very square angle, are slighter at the 

 point, and have a more pronounced terminal hook. In 

 coridon the end of the clasp is much wider at corresponding 

 parts of its length, and though the terminal teeth are very 

 similar, there are one or two more in coridon than in thetis J' 



The Eev. G. Wheeler, while regretting the unavoidable 

 absence of Mr. Tutt, said that he had formed independently 

 almost the same conclusions on the relationship of the two 

 species. Practically both have a similar range ; for it is not 

 known that coridon does not extend into Mauritania, and 

 their eastern and western limits are identical. Thetis, apart 

 from mere aberration, is a very constant species, the North 

 African being the only local race. Coridon is, also, except for 

 aberrational forms (including the margins of the upper-side, 



