108 * EXPLANATION OF PLATES. 



Platyceras primordialis. / d C? 



Tig. 28. A nearly entire individual. The specimen is of the medium size among those 

 in tiie collection. 



EUOMPHALUS? VATTCINUS. / 3 ^ 

 Fig 29. The upper side of the spire. The specimen is somewhat distorted. 



- Theca primordialis. / ^ i^ 

 Figs. 30 h 81. Fignrcs showing the opposite sides of the shell. 



Serpulites murchisoni. /. '^"o^ 

 Fig. 32. A figure of the natural size of the specimen. 



Ptychaspts granulosa. 



33. A figure of a small head, enlarged two diameters, to show the exterior 

 markings. 



34. A cast (;f a larger individual, natural size. 



35. A profile of the same in outline. 

 \Q. The head of a very small individual, enlarged three diameters. The specimen 



shows a hroader glabella iu front, with distinct eye-lobes on the fixed cheeks. 

 37 Si 38. Profile and lateral views of a cheek of tliis species. 

 39. A part of a thoracic segment. 



^40. A large pygidiuni. corresponding with the one referred to this species by Dr. 

 Owen. 



Specimens of the head of this species, at loast once and a half as large as fig. 34, 

 have been seen in the same association. 



Ptychaspis miniscaensis. 



a. 41. The glabella and fixed cheeks of an individual of mediiim size. 



42. A profile of the same. 



43. A much smaller head, given fur cojuparison with Ptychaspis granulosa, f. 34. 

 Fig. 44. A profile of the same. 



45. A cheek of this species, the figure of natural size. 



46 A pygidium of the same species. 



47. A segment of the body, found iu the same association, but probably belong- 

 ing to GflARIOCEPilALUS. 



Ptychaspis, sp.? 



The head of a very small individual of an undetermined species. It maj'- possibly be 

 the young of one of the above species. 



Chariogephalus whitpieldi. '-. ' 7 ,^~^ 



Fig. 49. The glabella and fixed cheeks, showing a curving frontal limb, and without 

 visible furrows in the glabella, which is a cast. Tlie figure of natural size. 



<« 50. A specimen preserving the glabella and fixed cheeks, where the frontal limb 

 is nearly straight. There are two pairs of furrows distinctly marked in the 

 glabella. The figure is twice the natural size of the specimen, 



«« 51. A }>rofile of the preceding specimen. 



♦« 62. A nu)vable cheek of this trilobite, natural size. 



«< 53. A smaller movable cheek of the same species. 



Agnostus josepha. 



Fig. 54. The head of this species, showing the short spines at the gostero-lateral 



angles. 



♦* 55. The pygidium of the same species. 

 These figures are enlarged three diameters. 



