BRACHIOPODA — TELOTREMATA. 



Fig. 390. Ati-ypa impressa, with interior of pedicle valve (Pal. N. V. IV.). 



316. A. spinosa Hall. (Figs. 391 and 392, d.) Devonic. 



Hinge line but little less than the greatest width of the shell. Sur- 

 face marked by strong, rounded, radiating costae which bifurcate at 

 unequal intervals and are crossed by strong concentric lamellae; 

 where these cross the costas they are often 

 produced into tubular spines. Differs 

 fromM. reticularis in the smaller number of 

 costae^and in^the longer and more nearly 

 straight hinge line. 



Onondaga-Chemung. Widely distrib- 

 uted throughout North America. 



Fig. 391. Atrypa spi- 

 nosa, a spineless individual 



317. A. hystrix Hall. (Fig. 392, e.) 



Devonic 



Differs from A. spinosa in its fewer, (Pal. N. Y. IV.) 

 coarse, rounded plication which are crossed 



by^lamellose lines of growth and occasionally prolonged into few 

 coarse spines. 



Chemung of New York, Pennsylvania, Iowa and Wisconsin. 



3 17^. A. hystrix var. occidentalis Hall. (Fig. 392,/.) Devonic. 



Gibbous, with few coarse plications and strong lamellose growth 

 lines but no spines. 



Middle Devonic of Iowa and Rock Island, 111. 



