230 PEOCEEDHiTGS OF THE GEOLOGICAL SOCIETY. 



this strange crustacean, in the ^ Transactions of the Eoyal Society 

 of Edinburgh ' for 1836 (vol. xiii. pi. 12). His species, by far 

 the largest in the genus, and probably not less than 3 feet long, 

 had been previously noticed, under the name of Idotea, by Dr. 

 Scouler, in the ^Edinburgh Journal of Natural Sciences ' for 1831. 

 Dr. Harlan too, in his ' Medical Researches,' had given similar, but 

 rather more perfect figures of two species from Williamsville, Buf- 

 falo, in the State of N^ew York. iJl these representations showed 

 that the Eurypterus possessed at least three pairs of appendages, of 

 which the hinder pair were dilated for swimming. More lately Dr. 

 Ferd. Eoemer gave a beautiful lithograph of the principal species in 

 Meyer's ' Palseontographica ' (vol. i. pi. 27) ; and Eichwald has 

 since published in the ' Bulletin of the Imp. Soc. Nat. Moscow ' for 

 1854 a complete series of illustrations of the Baltic species, K tetra- 

 gonophihalmus, Fischer, but under the name of E. remipes. The 

 number and character of the appendages are the same in this as in 

 the species previously published by Dr. Harlan. 



Now that the structure of Pterygotus^ is fully understood, and the 

 position of the eyes found to be lateral, and not on the surface of the 

 carapace, it is easy to distinguish that genus from Eurypterus by 

 superficial characters. There is, however, a further and very im- 

 portant difference in the small size of the antennae in the latter 

 genus : these are much shorter and slenderer than the swimming- 

 feet, and not larger than the palpi. These palpi are five- or six- 

 jointed, and furnished with only a minute smooth chela at the tip ; 

 while in Pterygotus the chelge are very large and armed with long 

 cutting teeth. 



A new and very remarkable form of Eurypterus has been lately 

 discovered in the middle beds of the Old Bed Sandstone of Brecknock- 

 shire. Only the carapace has been yet found ; but it is so strongly 

 marked and characteristic that there can be no difficulty in identi- 

 fying it. I propose to call it Eurypterus Symondsii, after the accom- 

 plished geologist who brought it under notice, and who has kindly 

 presented casts to the Museum of the Geological Survey. The ori- 

 ginal is, I believe, in the choice collection of the Malvern Natural 

 History Club, Malvern. 



EuEYPTEEus Symondsii, spec. nov. Plate X. fig. 1. 



The specimenf, of which we have only the exterior cast of the head, 

 perfectly representing the surface, however, is impressed on a slab 

 of brownish-grey micaceous grit, from the Upper Cornstones of Rowl- 



* Himantopterus (Salter, Quart. Journ. Geol. Soc. vol. xiii. p. 27) proves to 

 be the same genus as Pfer?/gotus, though probably a good subgeneric form ; but, 

 as the name has been preoccupied for a genus of insects, Erettopterus is proposed 

 in its place. The eyes are lateral in both subgenera; but they are long-oval on a 

 rounded carapace in Eretiopterus, and circular on a subquadrate carapace in 

 Ptery<jotus proper. There are some other diflPerences too, of subgeneric value, in 

 the form of the epistoma and labrum ; these will be more particularly described 

 in Monograph I., Memoirs of the Greological Survey. 



t See a notice of this specimen by the Hev. W. Symonds, in the Edin. New 

 Phil. Jom^n. new series, vol. vi. pp. 257, 313. 



