300 



TRENTON TRILOBITES. 



FIB. 213. 



of the lateral lobes extending from the axis more than half way to the margin; entire surface finely 

 punctulated. 



When the crest of the buckler is removed, a narrow shallow groove is visible at the base. 

 In young specimens the caudal extremity is more pointed, and presents the marks of eight anchylosed 

 articulations; in older specimens, these increase in number, but the external crust presents scarcely any 

 traces of them. When the crust is removed, however, they are often very distinct. 



Plate XII, Fig. 4, represents a specimen of Asaphus canalis, natural size, from Porter's Landing in 

 Grand Isle. This was the finest locality for the species, and for many other species of fossils that we have 

 seen in any part of the State. The A. canalis was found elsewhere at Larrabee's Point, Frost's Landing in 

 Bridport, half a mile north of Chimney Point in Addison. McNeil's Point in Charlotte, South Hero, 

 Grand Isle, north end of Isle La Motte in several places, and at Highgate Springs. 



Calymene. The form of the shield is oval; the head larger than the pygidium, and the latter is about 

 one half as large as the thorax; the crest is granulated; the front lobe of the head projecting, the lateral lobes 

 of the glabella are globular and separated from the middle part by deep winding furrows, which nearly isolate 

 them, the main furrows being divergent from the front; the eyes are reticulated, but not well developed; the 

 thirteen segments of the thorax are angulated, and the ribs or lateral lobes are bent and rounded at the ex- 

 tremities; the pygidium is convex and rounded, and its center lobe distinct and narrower thanthe lateral lobes. 

 Calymene senaria (Green.) Buckler semi-circular or sublunate, regularly rounded in front, or slightly 

 projecting in front of the glabella, with a distinct thoracic ring at the base; posterior angles subacute or 

 rounded; glabella separated from the cheeks by a deep broad groove, wider behind or often of nearly equal 

 width throughout, with three tubercles or lobes on each side, the anterior one often obscure; cheeks trian- 

 gular; eyes trunca to-conical, situated a little outward from the inner edge of the cheek; facial suture 

 terminating nearly in front of the eye; thorax with thirteen segments, those of the lateral lobes with a 

 deep groove extending from the base more than half way to the extremities ; caudal shield 

 small, with seven segments in the middle lobe and five in each lateral one, the latter with an 

 impressed line or shallow groove the whole length. 



Fig. 213 represents a small specimen of the Calymene senaria. It is found in most of the 

 localities of Trenton fossils in Vermont, particularly at Larrabee's Point, Chimney Point, 

 Frost's Landing, NcNeil's Point, South Hero, Grand Isle, and Isle La Motte (north end.) 



Ceraurus. Large or small ; form somewhat triangular ; pustulated, granulated, and 

 spinous ; cephalic shield crescentiform ; thoracic rings eleven ; glabella quadrangular and 

 four-lobed ; the furrows forming the lobes extend transversely one-fourth across them ; the 

 main furrrow, separating them from the cheeks, are nearly in a line with those on each side of the axis ; 

 eyes distant, granulated ; cheeks triangular. 



Ceraurus pleurexa.nthem.us (Green.) Buckler crescent form, with a prominent connate articulation at the 

 base, and the posterior angles extended into long curved spines; eyes small, distant, sublunate, granulated (not 

 reticulated) ; glabella clavate, more or less convex, deeply four-lobed on each side, leaving the front one broader ; 

 thorax with eleven articulations ; caudal shield with four (scarcely five) anchylosed articulations in the 

 axial lobe, and three on each lateral lobe, the upper of these articulations thickened and 

 extended into a long curved spine, the others terminating in blunt points ; surface 

 entirely papillose or granulated, the buckler with scattered larger tubercles ; two ranges 

 of small papilose tubercles along the central lobe, and three ranges of mammillary 

 tubercles on each lateral lobe; labrum ovate, attached to the front margin of the 

 glabella by a straight suture. No single specimen, yet found, presents all these 

 characters, but the description is derived from fragments of difierent individuals. 



Fig. 214 represents a nearly entire specimen of this species, but the maxillary 

 portions are obscure. Prof. Adams found this specimen in Vermont, but his notes 

 leave it uncertain whether it occurs in Shoreham, Bridport and Addison, or in 

 only one of these towns. 



Trinudeus. Form a short ellipse; surface smooth; head largely developed, and bordered with a perforated 



Calymene 

 seuaria. 



FIG. 214. 



Ceraurus 

 pleurexanthemus. 



