478 



Forty- fifth Report on the State Museum. 



most part, closed. This statement, however, is not true of 

 Chonetes where there is a single row of short marginal spines on 

 the cardinal margin of the pedicle-valve alone ; these cross the 



Fig. 46.— Portion of the shell of Siphono. 

 treta; enlarged. (Kutorga.) 



Fig. 47. — Schizambon 

 fissus. (Kutorga.) 



cardinal substance of the valve, have wide, internal openings and 

 are believed to be closed at their outer extremities. In Anoplia 



these tubular passages 

 T exist, but are not ex- 

 t ended into spines 

 (see Plate 20, figs. 15-19). 

 Some species of Siphon- 

 oTRETAand Strophalosia 



Fig. 48.— Chonetes scitula. Showing the tubes connecting 

 the hollow marginal spines with the interior of the shell; have tne Spines COlTUga- 



eniarged. ted. In a few genera the 



cuticular or outer layer of the shell bears a reticulated or tesselated 

 ornament, or series of coarse punctures arranged in quincunx 

 (Tkematis, Eichwaidia, Porambonites), or in radial rows(()RTnis, 

 Porambonites; Plate 6). The surface is often granulose, 

 especially in species which possess a punctated shell, and some- 

 times in other shells, as Spirifer. The genus Lept.ena is charac- 

 terized by coarse concentric wrinkles or undulations over the 

 horizontal or visceral area of the valves ; rarely there arc two 

 series of fine oblique concentric wrinkles, as in Chonopectus. It 

 has been observed that the greatest modifications of the exterior 

 occur on the pedicle valve, and this difference may be largely 

 explained by comparing the braehiopod with the bryozoan. If 

 the brachial or upper valve of the former corresponds to the 

 operculum of the latter, it is then the pedicle-valve which, as 

 above suggested, may he regarded as the cell or main receptacle 



30 



