4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



Middle Cambrian, Conasauga ; (loc. 112) 5 miles southeast of 

 Center, Alabama. 

 Lectotype and plesiofypes. — U.S.N.M. no. 61568. 



Acrocephalops nitida, n. sp. 



Acrocephalites insignis Walcott (part), Smithsonian Misc. Coll., vol. 64, 

 no. 3, p. 179, pi. 25, figs, la, lb, 1916. (Not fig. i = .-J. insignis.) 



Acrocephalites americanus Walcott, idem, pi. 24, fig. 3a. (This poor specimen 

 may represent the species.) 



Unfortunately, none of the illustrated specimens is well preserved, 

 and that shown in figure la has been damaged since it was photo- 

 graphed. However, this form clearly has weaker eye lines and other 

 sculpturing than A. insignis. 



Occurrence same as preceding. 



Cotypcs. — U.S.N.M. nos. 61569, 61570, and possibly 61560. 



ALOKISTOCARE Lorenz, 1906 



Alokistocare Lorenz, Zeitschr. deutsch. Geol. Gesell., vol. 58, no. i, p. 62, igo6. 

 Alokistocare Walcott, Smithsonian Misc. Coll., vol. 64, no. 3, p. 182, 1916. 

 Amccephalus Walcott, idem, vol. 75, no. 2, p. 53, 1924. 

 Amcccphahis Walcott, idem, vol. 75, no. 3, p. 65, 1925. 



If the rules of nomenclature did not require recognition of Alokis- 

 tocare because Lorenz named a described species as its type, the 

 original description would remain meaningless. Furthermore, the 

 choice of A. suhcoronatmn as the genotype is unfortunate because 

 only cranidia of the species are definitely known, and hence uncer- 

 tainty prevails as to whether the tail was small or large, which in 

 turn prevents final determination of generic Hmits. This problem 

 is further complicated by the fact that cranidia similar to that of the 

 genotype occur in entire specimens with both small and large pygidia. 

 However, a search among the scores of cranidia of A. snbcorouatum 

 from Blacksmith Fork, Utah, reveals the presence of two pygidia 

 which can represent the species, as they are small and similar to those 

 of other species here referred to the genus. 



Much confusion exists between Alokistocare and Acrocephalites as 

 well as among species of several other genera, because many strongly 

 bossed trilobites which appear to belong rightly to Alokistocare have 

 been assigned to the Atlantic Province genus Acrocephalites, and, as 

 discussed above, their removal leaves no North American species in 

 that genus. On the other hand, certain species must also be removed 

 from Alokistocare to new genera. 



Owing to the confusion of species, Alokistocare has not been prop- 

 erly understood, although in 1916 Walcott presented a diagnosis, evi- 



