ZOOPHYTA. 



Genus LITHOSTROTION, Fleminc 



O* 



LlTHOSTROTION MAMILLARE (?), Castleiiail, (sp.) 



PI. 1, Fig. 4, and 4 a, b. 



Sti/l ina, Lesueur. 1832. 



Astrcea mamillaris, Castlenau. Ter. Sil. de l'Amerique du Nord, pi. 24, fig. 5. 



1843. 

 Axinura Canadensis. Ibid., fig. 4. 



Acrocyathus floriformis, d'Orbigny. Prod, do Paloeont., t. 1, p. 1G0. 1850. 

 Lithostroiion basaltiforme, Owen. Bept. "Wiscon., Iowa, and Min., tab. iv, figs. 



5 and G. 1852^ 

 Lithostroiion mamillare, Edwards and Haime. Monog. Polyp., p. 433, pi. 13, figs. 



1 and 1 a, b. 

 Lithostroiion mamillare, Hall. Geol. Kept. Iowa, vol. i, part 2, p. 6G7, pi. 24, fig. 



5, a, b. 



1 have referred this coral to the above species with some hesitation, because 

 the specimens are imperfect fragments, not giving a very satisfactory idea of the 

 general appearance of the entire corallum, nor of the calices. As near as I have 

 been able to determine, however, from sections, it agrees well in its internal struc- 

 ture with fine specimens of L. mamillare, now before me, from Missouri and Illi- 

 nois. There can be no doubt in regard to its generic characters ; and, if not 

 specifically identical with the common species of the Mississippi valley, it is cer- 

 tainly a closely allied representative form. 



As in that species, the specimens present two modes of growth, one in which the 

 corallites are in closely aggregated masses, and assume an angular prismatic form, 

 and another in which they are less crowded, cylindrical, and grow in tufts. These 

 two forms may be distinct species ; but they seem to present the same internal 

 structure, and it is not improbable, that additional specimens would show inter- 

 mediate gradations in the mode of growth, as we see in authentic examples of L,. 

 mamillare from the Western States. 



In both of the forms alluded to above the rays vary from about twenty to thirty- 

 eight, most of which extend to the columella. Alternating with these is another 



(5) 



