STROPHALOSIA 143 



more narrowly rounded transversely across the median part of the pedicle 

 valve, in consequence of which the lateral slopes curve less abruptly to 

 the lateral margins, but a larger number of examples should be examined 

 to determine this as a constant character. The most essential difference 

 between the two species is in the character of the fine appressed spines 

 which are essentially uniform in size upon E. morbillianus with more 

 elongate bases, while in E. biseriatus the spine bases occur in two distinct 

 sizes, larger ones posteriorly upon each band with much smaller and more 

 numerous ones closely crowded anteriorly. 



A second example of the species is mentioned by Winchell, "a cast from 

 the Yellow Sandstone below (probably No. 5)," as being probably iden- 

 tical. A careful examination of the two specimens, however, clearly in- 

 dicates that they are not the same species, and furthermore the Yellow 

 Sandstone specimen is probably a Productella. 



Horizon. Base of Burlington limestone. 



Genus STROPHALOSIA King 



Description. Shells resembling Productus or Productella in general 

 form, with a distinct cicatrix on the umbo of the pedicle valve at the 

 point where they have been attached by the shell substance to some ex- 

 ternal object, or attached by nearly the entire outer surface of the pedicle 

 valve. Pedicle valve with a well-defined cardinal area, the delthyrium 

 closed by a deltidium, cardinal teeth prominent but not supported by 

 dental lamellae. Brachial valve with a narrower cardinal area, the car- 

 dinal process erect, bifid on its anterior and trifid on its posterior face, 

 supported laterally by the socket plates and continued anteriorly into a 

 median septum which extends half the length of the valve. Surface of the 

 pedicle valve spinose, the spines near the beak often recurved and em- 

 bracing some external object, and in some species all the spines assisting 

 in the attachment of the shell. Brachial valve either spinose, lamellose, or 

 smooth externally. 



Remarks. Among the species which have been referred to the genus 

 Strophalosia in the present report are two rather distinct types. One of 

 these contains small species, such as S. scintilla and S. keokuk, which are 

 attached to other brachiopod or mollusc shells by essentially the entire 

 outer surface of the pedicle valve, the surface spines being little root-like 

 processes which grow outward from the shell margin in all directions in 

 close attachment throughout their entire length. The other type of shell 

 is larger and was attached during life by the umbonal portion of the 

 pedicle valve only, being represented by the two species 8. cyiribula and 

 S. beecheri. 



