216 BULLETIN OF THE 



into consideration, and with them the thought of the variation of the 

 appendages that must necessarily correspond in a greater or less degree, 

 the force of the above statement is very striking, and may equally be 

 applied to the class under consideration. Such diverse forms as are 

 found in the genera Asaphus, Cali/mene, Deiphon, Heiyiopleurides, 

 Ilarpes, Agnostics, and other genera, — the compact, small hypostoma 

 of Ogygia Biichii,* and the long-forked hypostoma of Remopleurides 

 striatidus, extending back to beneath the sixth thoracic segment,t — 

 the twenty-six segments of the thorax of Ilarpes xcngida,% and the 

 two of Agnostics, — the large massive pygidium of Asaphus or £roiv- 

 tens and the limited area of the same in Paradoxides or Meniopleuri- 

 des, and all the varying intermediate forms, — afford ample material for 

 those inclined to theoretically reconstruct the animal, and also for the 

 palaeontological investigator. 



The two forms used to illustrate the results of the present investiga- 

 tion are much alike in some respects, as the head and thoracic regions 

 differ but little. There are certain differences, however, that are quite 

 marked. The legs of Calymene are more slender, and less apt to be 

 straightened out. The joints are also more cylindrical. The branchiae 

 are more delicately constructed, and usually better defined than in 

 Ceraurus. Sections cut from either species are very readily distin- 

 guished one from the other by the general appearance of the cephalic 

 appendages, the legs, and branchiae. 



Ova of the Trilobite. — Plate IV. fig. 8 is an illustration of a 

 median, longitudinal section of a Ceraurus in which the cephalic 

 cavity and a portion of the thoracic cavity are preserved and filled with 

 calcspar. The small elongate-oval and round spots seen in the spar, in 

 the posterior portions of the cephalic cavity and the anterior thoracic 

 cavity, are somewhat enlarged in Fig. 8 a, and their arrangement 

 shown as when imbedded in the spar. To the groups of ova illustrated 

 by M. Barrande§ they have a strong resemblance, and there is little 

 doubt but that these small cylindroid bodies were the ova of the 

 Trilobite, as there is nothing to lead to the view that they are of con- 

 cretionary origin. II 



• Sil. Sys. Boh., I. Plate 2 A, fig. 26. 

 t Cincinnati Jour. Sci., IL p. 347. 

 X Sil. Sys. Boh., I. Plate IX. fig. 1. 



§ Sil. Sy.s. Boh., I. Supplement, Plates II., XVIII., and XXXV. 

 II See 3l3t Report N. Y. State Museum Nat. Hist., Note on the Eggs of the 

 Trilobite. 



