ARACHNIDA— SYNXIPHOSÜRA 



.p.e. 



at least nine in number; the telson not observed in any specimen thus far 



discovered. Axial portion of abdomen diminishing rapidly from before 



backwards. This geniis has been understood 



as connecting the Xiphosura with the Synxi- 



phosura. Silurian ; Scotland. Ty^Q, N.falcatus 



Woodw. 



Bunodes Eichw. (Exapmurus Nieszk.) (Fig. 

 1502). Cephalothorax semicirciilar, convex, 

 with radial furrows 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. 



Hejniaspis Woodw. (Limuloides Salter) (Fig. 

 1503). General form similar to that of Bunodes. 



Cephalothorax one-half 



as long as broad, with 



several genal spines ; 



central portion well de- 



fined. Postcephalic Seg- 

 ments nine in number, 



besides the acuminate 



telson, more or less dis- 



tinctly divided into two 



Fig. 1502. 



Fig. 1503. 

 Hemiaspis limuloides Woodw. 



Bunodes lunula, var. schrenki, Niesz. 

 Silurian ; Rootziküll, Oesel. Drawing 

 made from a plaster model, as restored by 

 re^ions (mesosoma and hatten, 2/1. Pros, Prosoma ; Ms, Meso- 

 " \ 1 • 1 soma, füllowing wh ich are the four narrow 



metaSOma), SUbtriangUlar somites and telson constltuting the meta- 

 in mifli'nP nnrl witli n ^°"^* ' ^^' I^'i^eral eye; pe, Parietal eye. 

 in outline, ana Wltn a (Supposed antennae omitted.) 



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 narröwer and longer than the preceding, their 



knd"^"Äo:?te^^^^^ 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. 



Pseiidoniscus 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 



