504 Mr. R. I. Pocock 07i the MorjyJiohgy 



LXX. — Soine Points in the MorphoJoqij and Classification of 

 the Opiliones. By R. I. PococK. 



[Plates IX. & X.] 



Part I. — The Classification of the Plagiostetsi. 



In 1873 Sorensen (Nat. Tidskr. (3) viii. pp. 514-515) 

 classified tlie Oi)ilionides into two tribes — Opilioiiini for the 

 typical genera, and Trognlini for IschyropsaJis, Nemastoma, 

 Dicranolasma, Trogulus^ and allied forms. From this classifi- 

 cation it may be inferred that in the opinion of its author 

 Ischyropsalis is more nearly related to Nemastoma and Trogu- 

 lus than to the Phalangiine Opiliones, or Opilionini genuini as 

 Sorensen called them. Subsequent authors have apparently 

 been unable to divest themselves wholly of this view of the 

 matter. 



Three years later Thorell propr)sed the following classifi- 

 cation (Ann. Mus. Genov. viii. pp. 4G2-469, 1876) : — 



Fam. I. Phalangioid^. 



Fhalcmgium &c. aud Sderosonia. 



Fam. II. Nemastomoii)^. 



Subfam. 1. Neniastomini. 

 A. — a. Ischyropsalis. 



h. Ne^nastoma, 

 B. Dicranolasnut. 

 Subfam. 2. Trogulini. 



Trognltis aud Anelasma. 



This classification, an expansion of Sorensen's, involves 

 the supposition on Thorell's part that Ischyropsalis is more 

 nearly related to Trogidus than to Phalangium, since the two 

 forms are classified together in a group equal to the group 

 containing Phalangium and its allies. The association, 

 moreover, of Ischyropsalis with Dicranolasma in one sub- 

 family, contrasted with another containing Troguhis, attests 

 the belief that Dicranolasma is more nearly allied to Ischy- 

 ropsalis than it is to Trogulus. 

 ' Both these conceptions are unquestionably erroneous. 



Simon, in 1879 (' Arachnides de France,' vii.), in an 

 excellent treatise on the Opiliones of France, with stray 

 notes upon exotic forms, proposed the following taxonomy of 

 the genera : — 



