Afiijnals found in the Mitchehtoivn Cave. 29 



Abdomen very pale greenish. Epigyue of female with large cavity, 

 front margin rounded, hind margin straight, with small central pro- 

 minence (fig. 3). 



M. Simon describes thirteen species of this genus, of which no less than 

 five are inhabitants of caves, while most of the others are found under 

 stones and in similar concealed situations. A colony of a British species, 

 P. micropthhahman, Cb., was found in i860, by Dr. Meade, ^ established at 

 the bottom of a Durham coalpit. Quite recently, ^ Rev. F. O. P. Cam- 

 bridge has recorded P. egeria from the Somerset cavern known as Wookey 

 Hole, and remarks that sometimes the hinder, sometimes the front pair 

 of central eyes, are aborted. P. egeria has, however, been taken in 

 numbers near Edinburgh, ^ running on railings in sunshine, and thus 

 appears to live indifferently above or underground. P. myops, on the 

 other hand, seems a true subterranean species. It is very nearly allied to 

 P, egeria, but may be distinguished by the characters of the male palp, 

 given above. Moreover, P. egeria has three spines on the first, and two on 

 the second femur. It is also a somewhat larger spider than P. niyops, and 

 decidedly less pale and washed out in appearance. Even the specimens 

 from Wookey Hole (a pair of which Mr. F. Cambridge has generously 

 sent me for comparison) do not show the sickly aspect which charac- 

 terises P, 7nyops from the Mitchelstown cavern. 



The excessively small eyes of this spider, and their tendency to become 

 altogether obsolete, are in accordance with the subterranean dwelling 

 place. The small size of the eyes is, however, characteristic of the entire 

 genus, even for those species which live in the open air. 



It is remarkable that the underground species oiPorrhomnia are omitted 

 from the list of European cave animals given in Prof. Packard's exhaus- 

 tive memoir upon the cave-fauna of North America.* There is, however, 

 a spider described (by Mr. J. H. Emerton) in that memoir under the 

 name of Linyphia incerta, which certainly belongs to the genus PorrhommUy 

 and is, I believe, identical with our Mitchelstown P. jnyops. Mr. Emer- 

 ton's figures of the male palpal organs of his species show the regular 

 conical apex of the bulb and the two curved apical spines which charac- 

 teirise those organs in P. myops. If a comparison of types should justify 

 this opinion, Mr. Emerton's name, having been first published in 1875,^ 

 will take priority of M. Simon's, and our species will have to be known as 

 Porrhomma ijtcerta. This North American -spider — which, at any rate, is 

 extremely near the Mitchelstown species — has occurred in the Fountain 

 Cave, V'irginia, and in the Bat Cave, Kentucky. Mr. Emerton states that 

 in different individuals a variable number of the central eyes may be 

 wanting. 



1 Zoologist, i860. 



2 Ann. Mag. Nat. Hist. (6), vol. xv., 1895, p. 36, pi. iv., fig. 13. 



2 Proc. R. Phys. Soc. Edin., 1894, p. 560. 



* Mem. Nat. Acad. Set. (Washington), vol. iv., 1888. 



^ Amer. Nat., vol. ix. 



