1866.] WOODWARD — ^TRUCTUHE OF XIPHOSTTHA. 37 



Trias, 7 in the Oolitic, 1 (doubtful) in the Chalk, and 1 in the Ter- 

 tiary; and there are 4 recent species. 



They occur living in the East Indies, in Japan, and on the east 

 coast of IN'orth America — and fossil in I^orth America, Great Britain 

 and Ireland, Scandinavia, Eussia, Poland, and Germany. 



EXPLAIN ATION OF PLATES I. & H. 



Illustrative of the Structure of the Xiphosura and Eurypterida. 

 Plate I. 



Fig. 1. Belinurus regince^, Baily. Coal-measures, Queen's County, Ireland. 

 H. = Head; Th.= Thorax; Ab. = Abdomen ; T.=Telson. 



2. Frestwichia {Limulus) rotundata, Prestw. sp. Coal-measures (Penny- 



stone ironstone), Coalbrook Dale. 



3. Hemiaspis limuloides, H. Woodw. Lower Ludlow shale, Leintwardine. 



(From the late Mr. H. Wyatt-Edgell's collection.) 



4. Bunodes limida, Eichw. Upper Silurian, Isle of QEsel, Baltic. 



5. Pseudoniscus aculeatus, Xieszk. Upper Silurian, Isle of CEsel, Baltic. 



6. Exapinurus SchrenJcii, Isie&zk. Upper Silurian. Isle of (Esel, Baltic. 



(Figs. 4-6 are copied from Dr. Kieszkowski's paper in the Archiv fiir 

 die Naturk. Liv-, Esth., und Kurl.-erste Serie, zweiter Bd. tab. ii. 

 figs. 12, 13, & 15, pp. 378-382. Dorpat, 1859.) 



7. Eurypterus remipes, Dekay. Upper Silurian, New York. (Copied 



from Hall's ' Palaeontology of !Psew York,' vol. iii. pi. Ixxxiv. a. fig. 1.) 



Plate II. 



Fig. 1. Caxdi^diCe oi Limulus poly phemus {recent). East coast of ISTorth America. 

 Showing the larval and compoimd eyes. H.=Head; Th.= Thorax; 

 Ab.= Abdomen; T. = Telson. 



2. Underside of same, showing indications of the coalesced thoracic and 



abdominal somites, and the processes for the attachment of the appen- 

 dages. 



3. The first stage of Limulus (yoimg), dorsal aspect. 



4. Underside of the same, enlarged (after Milne-Edwards). 



5. Club-shaped antenna of male Limulus. 



6. Chelate antenna of female Limulus. 



7. Operculimi of receat Limulus. r, reproductive apertures. 



8. Operculum of Eurypterus (Hall). 



9. Chelate antenna of Fterygotu^. 



10. Simple antenna of SUmonia. 



11, Specimen from Lanarkshire in the British Museum collection (reduced to 



one-fourth), showing two thoracic plates of SUmonia associated together. 



December 5, 1866. 



C. J. H. AUen, Esq., F.Z.S., 4 Park Crescent, N.W. ; Henry 

 Pitts Cassidy, Esq., Engineering College, Poena; Eobert Etheridge, 

 Jun., Esq., of the Geological Survey of Victoria, Australia ; Marshall 

 Hall, Esq., 3 Cleaveland Terrace, Hyde Park, W. ; Alfred Gutteres 

 Henriques, Esq., F.Z.S., Stone Buildings, Lincoln's Inn, "W.C. ; Henry 

 Lainson, Esq., Heath House, Eeigate, Surrey ; Dr. James Murie, 

 20 Eegent's Park Eoad, N.W. ; and John W. Pike, Esq., Mining 

 Engineer, Mexico, were elected Fellows. 



* Ann. & Mag. Nat. Hist. 1863 (3rd Series), vol. xi, p. 107, pi. v. 



