634 



ARTHROPODA 



SUB-KINGDOM VII 



Family 1. Encrinuridae. Linnarsson. 



Cephalon narrow, transverse. Fixed cheeks very large. Free cheeks long, narrow, 

 separate, sometimes with a free rostral plate between the anterior extremities. Sutures 

 extending from in front of the genal angles obliquely forward, and cutting the anterior 

 margin in front of the glabella. Eyes very small or absent. Thorax of from nine to 



FIG. 1317. 



Cephala -of Proparia. A, Placoparia. B, Encrinurus. C, Calymmene. D, Dipleura. E, Cheirurv.s (Eccop- 

 tocheile). F, G, Dalmanites. H, Chasmops. I, Acaste. J, Phacops (after Beecher). 



twelve segments, with ridged pleura. Pygidium generally composed of many segments ; 



limb with strong ribs usually less in number than the annulations of the axis. Ordo- 



vician and Silurian. 



Encrinurus, Emmrich (Cromus, Barr.), (Figs. 1262, 1317, 5-1319). Cephalon 



tuberculated ; glabella pyrilbrm, ])romineiit ; 

 free cheeks narrow, separated in front by a 

 small rostral plate ; eyes small, elevated on 

 conical prominences ; thoracic segments eleven ; 

 pygidium triangular, numerously segmented, 

 limb with fewer ribs. Ordoviciaii and Silurian ; 

 Europe and America. 



Placoparia, Corda (Fig. 1317, A). Glabella 

 more strongly lobed than in Encrinurus ; eyes 



obsolete ; free cheeks long, narrow ; thorax of twelve segments ; pygidium small, with 



few segments. Ordovician ; Europe. 



FIG. 1318. 



E-ncrinurus punc 

 tatus, Eminr. Sil 

 urian ; Gottland. 



FIG. 1319. 



Encrinurus Bohemians, 

 Barr. Silurian (Et. E); 

 Lochkow, Boheinia. 



Family 2. Calymmenidae. Brongniart. 



Cephalon somewhat wider than long. Fixed cheeks large; genal angles rounded or 

 produced into spines. Glabella narrowing anteriorly. Free 

 cheeks long, separate, usually with a free plate between the 

 anterior extremities. Sutures extending from just in front of 

 the genal angles, converging anteriorly, and cutting &he margins 

 separately. Eyes small, facets numerous, visual surface seldom 

 preserved. Thorax of thirteen segments, with grooved pleura. 

 Pygidium of from six to fourteen segments; axis tapering. 

 Ordovician to Devonian. 



Calymmene, Brongt. (Figs. 1317, C, 1320). Body oval in 

 outline, possessing ,the power of enrolment to perfection ; 



TV -n -i -1 T-ij-i.-i c 



glabella conical, strongly convex, divided by three pairs of 

 deep lateral grooves ; eyes small ; hypostoma quadrate, 

 notched. Thorax of thirteen segments, axial furrows deep ; pygidium of from six to 



FIG. 1320. 



Cnlyminene srnaria, Conrad. 

 Ordovician ; Cincinnati, Ohio. 



