350 PROCEEDINGS OF THE ACADEMY OP [1881. 



structure with Batocr. Indiansensis and B. Christyi^ but has 

 spatulate arms and a very different arm formula. It is of the 

 type of Eretmocr. originarius with which it is more closely 

 allied than would appear at first sight. E. adnltus is larger and 

 especially broader, but this is evidently due to the double arm 

 structure which required those modifications, the differences are 

 similar to those between Batocr. Lovei and B. trocht^cus. 



Geological Position, etc. — Keoknk limest. Canton, and Ed- 

 wardsville, Ind. Collection of Chas. Wachsmuth. 



24. DORYCRINUS Roemer. 



1854. F. Roemer. Archiv f. Naturgesch., Jahrg., xix, Band i, p. 307. 



1855. F. Roemer. Lethaia Geogn. (Ausg. 3), p. 249. 



1869. Meek and Worth. Proc. Acad. Nat. Sci., Phila., p. 165. 

 1873. Meek and Worth. Geol. Rep. 111., v, p. 379. 



1879. Zittel. (Subgenus of AmpJwracrinus). Handb. d. Palaeont., 1, p. 370. 

 Syn. Amphoracrimis Meek and Worth, (not Austin;, 1866, Geol. 



Rep. 111., ii, p. 209. 

 Syn, Actinoerinus {Amphoracr.) Meek and Worth., 1861, Proc. 



Acad. Nat. Sci., Phila., p 132. 

 Syn. Sphmrocrinus Meek and Worth., 1865 (not Roemer, 1851). Ibid., 



p. 154. 

 Syn. Ccelocrinus Meek and Worth., 1865 (not Caliocrimis White, 

 1863). Ibid., p. 273 ; and 1868, Geol. Rep. 111., ii, p. 215. 



Roemer 's tj'pical species of Dorycrinus is provided with six 

 large spines at the vault, and upon this peculiarity, principally, 

 the genus was founded. In regard to this point the genus must 

 be amende'd, as there are other species, evidently belonging to the 

 same group, which have only a central spine, others have three, 

 and still others in place of the spines a large convex or nodose 

 plate. There are, however, other excellent distinctions which 

 make Dorycrinus a good genus. 



Neither Hall, Shumard, de Koninck and Lehon, Pictet, nor 

 Schultze, have recognized Dorycrinus.^ all referring the species to 

 Actinoerinus, with which it agrees onlj^ in the general family 

 characters, and in having the rays extended into lobes. Dory- 

 crinus inclines far more toward Batocrinus and Eretmocrinui<. 

 with which it agrees in the general form of its plates, and in the 

 peculiar double arm structure, which became here a constant 

 character. It differs, however, ver}^ essentially in the lobed form 

 of the body, its strongly expressed bilateral symmetry, in the 

 lateral position of the anus, and in its opening out directly through 



