486 NORTH AMERICAN INDEX FOSSILS. 



also variable in size and form. Ambulacra long, nearly parallel- 

 sided, reaching to the base of the cavity, always impressed at their 

 upper ends. Lancet plates narrow, not filling the furrows, and 

 more or less exposed throughout two thirds of the ambulacra. 

 Side plates transversely elongate. Outer side plates usually well 

 developed. Hydrospires pendent, usually but two or three folds 

 on each side of an ambulacrum, the inner one forming a well- 



FiG, 1799- ^y Grana^ocn'mts norwoodz, summit {central part), X 2 ; 3, Cryptohlastus 

 melo, summit view, X 3- (After Eiheridge and Carpenter. ) 



defined hydrospire plate. Spiracles five, oval or round, piercing 

 the apices of the deltoids. Posterior spiracle larger, including the 

 anus. Summit closed by minute pieces which rarely exhibit any 

 definite arrangement. Column round. Surface ornamented with 

 rows of granules. Mississippic. 



24. G. neglectus Meek and Worthen. Mississippic. 



Small (height usually less than one third inch), and base five- 

 lobed. Spiracles not rising into tubes. 

 Burhngton of Missouri and Iowa. 



25. G. norwoodi Owen and Shumard. (Figs. 1792, c, 1799, a.) 



Mississippic. 



Calyx globose or elliptical-globose. Basal cavity deep and 

 funnel-shaped. All spiracles except the anal extended into erect 

 tubular openings. (Type of genus.) 



Burlington of Missouri, Illinois and Iowa. 



XL CoDASTER McCoy. 

 Calyx inverted, conical or ovoid. Base obtusely trilobate or 

 tapering more or less acutely. Summit usually broad and either 

 truncate or slightly convex and presenting a stellate appearance 



