86 Eev. F. O. Pickard-Cambridge on 



2. Digital joint scarcely at all prominent on 

 tlie upperside near the base. Palpal 

 organs exhibiting at the base on the inner 

 side and beneath a stout, conical, 

 squarely truncate prominence, directed 

 backwards and recurved inwards and 

 upwards M. sublimis, Cambr. 



b. Eyes of posterior row not equidistant; the 

 centrals of the row separated from each 

 other by a distance greater than that sepa- [Cambr. 



rating each from the adjacent lateral eye. . M. innotabilis, 



Neriene decora, Cambr., which I have been unable to 

 examine j must be closely allied to subtilis, Cambr., while 

 Neriene mollis, Cambr., is closely allied to rurestris, C. K. 



Good opportunities having lately offered themselves of 

 examining a great number of recently captured specimens of 

 the two very closely allied species Tmeticus bicolor, Bl., and 

 Tmeticus concinnus, Th., I venture to give figures and a 

 short description of those characters which seem to be most 

 serviceable for distinguishing the two. 



At first sight the two species appear to be merely extreme 

 varieties in point of size of one species, and it will scarcely be 

 finally settled as to whether the species be physiologically 

 distinct and thus fulfil all the criteria of true species, until it 

 be shown that those described under concinnus. Th., either 

 do not pair with, or, if they do, are unfertile with those 

 described under the name bicolor, Bl. 



There is every variation in the size of the spiders and the 

 position of the eyes, the height of the clypeus, and the spines 

 beneath the tibise of the first two pair of legs, peculiarities of 

 structure which form very good distinctive characters if com- 

 pared in two specimens standing at the extreme opposing 

 ends of the line, yet so variable themselves in intermediate 

 forms as to render it almost impossible to say of many speci- 

 mens whether we have before us examples of concinnus, Th., 

 or bicolor, Bl. 



One would be inclined to suppose that in cases like these 

 we have before us excellent examples of that stopping-out 

 process of linking characters which is carried on by the 

 various selective influences, whether physiological or environ- 

 mental, amongst a series of individuals originally of one stock 

 now in process of being broken up into the groups which form 

 what science knows as distinct species. 



The characters given below are very variable. The most 



