Silurian Fossils. 



319 



Figs. 6 and 1 represent a fossil found in the Chazy limestone. 

 In general shape it somewhat resembles a Pleurotamaria, but it is 

 nearly flat above, and covered with striae across the whorls, which 

 are interrupted along the centre of the upper part of the whorl 

 by a concentric elevated line, as seen in Fig. 6. Good specimens 

 of this fossil are rare. 



The generic name is from the Greek raphe, a seam or suture, 

 and stoma, a month, from the suture or seam like appearance in 

 the upper side of the aperture. 



The specific name appears to be from the Latin stamineus, 

 made of threads, or full of threads, thready, probably having refe- 

 rence to the thread-like strige on the surface of this fossil. 



Fig. 9. 



Fig. 10. 



Fig. 9. Halysites catenulates, or Catenipora cscharoides» 

 Fig. 10. Homolonotus delphi?tocepalus. 



Lingula quadrata, Fig. 8, is one of the largest fossils of this 

 genus known. Its length is about an inch, its sides nearly par- 

 rallel, extremities rounded, and the surface covered with strong 

 concentric strise, with longitudinal striae extending from the top 

 to the bottom. It occurs in the Trenton limestone and Hudson 

 River group, and is found in the lower Silurian rocks of Europe. 

 The specific name, quadrata, has allusion to the somewhat four 

 sided shape. 



The chain coral, Halysites catenulatus, is one of the most com- 

 mon of the Silurian fossils both in Europe and in America. It 

 consists of numerous irregular vertical plates joining together so 



