310 B. I, POCOCK. 



recent scorpions bea,rs the pectines and has no appreciable 

 sternal area. 



But there appears to me to be no reason for regarding this 

 so-called sternal area other than as the pleural membrane of 

 the second somite of the mesosoma. 



Mr. Whitfield could find no satisfactory evidence for the 

 existence of stigmata, and infers from this fact, and from the 

 nature of the strata in which the specimen was preserved, 

 that the species was '"' aquatic in habits," and furnishes a 

 "liuk between the true aquatic forms like Eurypterus and 

 Pterygotus and the true air-breathing scorpions of recent 

 periods/' 



Of Paheophonus loudonensis, described by Laurie, 

 from the Upper Silurians of the Pentland Hills (' Tr. Royal 

 Soc. Edinb.,' xxxix, p. 576, pi. i, fig. 1, 1889), little need be 

 said, the specimen being too imperfectly preserved to yield 

 satisfactory data for discussion. That the specimen was 

 specifically distinct both from P. n unci us and P. Hunteri 

 cannot be doubted if the great length of the carapace and 

 the slenderness of the tail in the fossil are not attributable to 

 imperfection of preservation. As in P. Hunteri, there are a 

 pair of median eyes close behind the fore border of the cara- 

 pace, which is emarginate. 



No genuine stigmata were discovered, but on some of the 

 mesosomatic somites a curved ridge running obliquely out- 

 wards and backwards on the sides of the segments was 

 traceable. The ridge on the second somite Laurie inter- 

 prets as the impression of the outline of the pecten, those 

 on the others as the outline of a plate-like gill-bearing 

 appendage. 



4. Recapitulation. 



From a morphological point of view, perhaps the most 

 important results obtained by the examination of this fossil 

 ai'e those connected with the structures of the basal segments 

 of the prosomatic appendages, and their relation to the 

 sternal area of this region, and those connected with the 



