CLASS II 



ARACHNIDA— SYNXIPHOSURA 



N, p. f* 

 / 1 1 



at least nine in number 



discovered. Axial portion of abdomen 



backwards. This genus has been understood 



as connecting the Xiphosura with the Synxi- 



phosura. Silurian ; Scotland. Type, N.falcatus 



Woodw. 



Bunodes Eichw. [Exapinurus Nieszk.) (Fig. 

 1502). Cephalothorax semicircular, convex, 

 with radial furroAvs from the median portion. 

 Facial sutures obscure, converging from the 

 posterior to the anterior margin. According to 

 Patten's interpretation, a median ("parietal") 

 and a pair of lateral eyes are present, but no 

 genal spines. Abdomen divided into an an- 

 terior portion (mesosoma or " thorax ") consist- 

 ing of six trilobite-like segments having a broad 

 median axis and lamellar pleura with diagonal 

 pleural lines ; and a posterior portion (meta- 

 soma or " postabdomen ") of four narrow seg- 

 ments, besides a long and acuminate telson. 

 External surface of carapace and somites pus- 

 tulose. Silurian ; Oesel. 



Hemiaspis Woodw. (Lmuloides Salter) (Fig. 

 1503). General form similar to that of Bunodes. 



Cephalothorax one -half 

 as long as broad, with 

 several genal 

 central portion 

 fined, 

 ments 

 besides 

 telson, 

 tinctly 



the telson not observed in any specimen thus far 



rapidly from before 



diminishing 



regions 



Fio. 1502. 



Bunodes lunula, var. schrenki, Niesz. 

 Silurian ; Rootzikull, Oesel. Drawing 

 made from a plaster model, as restored by 

 Patten, "-/i. Pros, Prosonia ; M.<, Meso- 

 soma, following which are the four narrow 

 somites and telson constituting the meta- 

 sotna ; le, Lateral eye ; pe, Parietal eye. 

 (Supposed antennae omitted.) 



spines ; 



well de- 



Postcephalic seg- 



nine in number, 



the acuminate 



more or less dis- 



divided into two 



(mesosoma and 



metasoma), subtriangular 



in outline, and with a 



broad median axis which 



tapers gradually from before backwards. Pleura flat 



and short, the lateral margins of the sixth divided into 



two lobes, as if compound. Segments seven to nine 



are narrower and longer than the preceding, their 



combined length equalling that of the tail-spine. 



Silurian ; Scotland. 



Bunodella Matthew. Prosoma small, postcephalic segments seven in number, 



tapering posteriorly. Axial portion of the body elevated ; telson not observed. 



Silurian ; New Brunswick. 



Pseudoniscus Nieszk. (Fig. 1504). Prosoma relatively large, convex, 

 hippocrepiform, probably eyeless and without facial sutures ; genal angles 

 extended into short spines ; surface obscurely marked with radial furrows. 

 Postcephalic portion ("abdomen") strongly trilobed and trilobitiform, with 



Fig. 1503. 



Hem iaspis Vniiuloides Woodw. 

 SiluriaTi ; Leintwardine, Eng- 

 land. Vi (after Woodward). 



