490 PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [June 7, 



5. On a new Genus of Euetpterida from the Lower Lxtdlow Rock of 

 Leinxwardine, Shropshire By Henry Woodward, F.G.S., F.Z.S. 



(Plate XIV. figs, la, lb, & 7c.) 



The specimen which forms the subject of this paper is in the Mu- 

 seum of Practical Geology, Jermyn Street, and through the kindness 

 of Professor Huxley I have been permitted to describe it. 



Its discovery was referred to by Mr. J. W. Salter, in 1857 (under 

 the MS. name of Limuhides), in the ' Annals and Magazine of Natu- 

 ral History,' in a paper " On some New Palsecjzoic Starfishes," but the 

 genus has never yet been described (except by myself at the British 

 Association, Bath, 1864). The great interest attached to this new 

 Crustacean is, that it appears to offer just the link we needed to 

 connect the Xiphosura with the Eurypterida. 



Limuli, apparently differing but little as regards the carapace 

 from the recent species of China and America, occur as early as the 

 deposition of the Solenhofen limestone of Bavaria ; and in the Coal- 

 measures of England and Ireland several species of BeUinuri occur, 

 in which the cephalic shield is composed of the cephalo -thorax ; and 

 the segments of the abdomen if not anchylosed in all, are so in most. 



But in the specimen under consideration we have the cephalic, 

 thoracic, and abdominal divisions still remaining distinct, and appa- 

 rently capable of separate flexure. This important character at once 

 separates it from Limulus and Bellinurus. 



I have on this account (with the concurrence of Mr. Salter) consi- 

 dered his MS. name of Lhmdoides inappropriate as a generic appel- 

 lation, and adopted the name of Ifetniaspis (from i\jii(tvs, half, and 

 aiTTTts, a shield), reserving Mr. Salter's name of Limuhides for the 

 specific title of the most perfect specimen of the genus (see Plate 

 XIV. fig. 7«). 



But it will be observed that Hemiaspis is also, in general appear- 

 ance, strongly severed from the other species of Eurypterida, as well 

 as from the Xiphosura, in structure. 



The three divisions into head, thorax, and abdomen are more 

 strongly marked. The abdomen is reduced to very slender propor- 

 tions (less than one-third the breadth of the thoracic plates). The 

 telson is nearly one-third the length of the animal (the entire speci- 

 men measuring 2^ inches in length by 1 inch in width). 



The carapace in general outline resembles Limidus, but is more 

 dilated laterally. There is a faint indication on one side of the shield 

 of a facial suture, with a small aperture upon its border, as if to 

 indicate the position of the eye, but it is by no means clearly defined. 



The glabella (when perfect) appears from a second specimen to 

 have been ornamented with a semicircle of nine tubercles, and a 

 tenth immediately within the circle upon the elevated front, and 

 two small tubercles at the posterior margin. 



Four ray-like corrugations descend on either side of the glabella 

 towards the margin of the shield, and the whole surface of the cara- 

 pace is minutely tuberculated. The lateral margins of the shield 

 are ornamented with minute spines, and the two posterior angles of 



