1913] The Ottawa Naturalist. 139 



nostus, Jaekel, has the same type-species, .4. Icevigatus, Dalman, 

 as Lejopygc, Corda. In none of these cases can there be any 

 reason for accepting the new names proposed by Jaekel. Two 

 of the other new genera founded by Jaekel were based on new 

 species, but they seem, nevertheless, to be synonyms of two of 

 Corda's genera. Jaekel proposed to found the new Leiagnostus 

 on his species, L. erraticus, associating with it Agnostus nudus, 

 and others. Corda's genus Phalacroma, with A. bibullatus, 

 Barrande, as the type, includes .4. nudus, and Jaekel 's L. erraticus 

 has the same generic characters, so that there is no reason to 

 displace Corda's old name. Metagnostus, Jaekel, was founded 

 on another new species, named by him M. erraticus. This 

 species differs in very minor characters from ,4. glabratus, 

 Angelin. Metagnostus erratic us and .4. glabratus have the same 

 short glabella with faint basal lobes, and the same type of pygid- 

 ium, as Agnostus tardus, Barrande, which is the type of Arthrorh- 

 achis. Corda, and Metagnostus therefore seems superfluous. 

 Unfortunately, Paragnostus, Metagnostus, and Leiagnostus are 

 the genera which Jaekel considered typical of three of his new 

 families, and their rejection forces the rejection of the familv 

 names derived from them. Corda's family name Phalacromidce 

 would apply to the Icevigati, and, using the same types as Jaekel 

 the Paragnostida w T ould become the Condylopygidaz , and the 

 Metagnostidce would be transformed into the Arthrorhachidcc. 



Barrande , :; Walcott, 4 and Lake' have pointed out that 

 Microdiscus, Emmons, was founded on an immature specimen 

 of Cryptolithus (Trinucleus), and is not, therefore, at all the 

 Microdiscus of Salter, Walcott, and authors generally. Walcott 

 has suggested that Pemphigaspis, Hall,' 1 may be the same as 

 what is generally meant by Microdiscus, and so take its place, 

 but he has not followed this course himself. The w 7 riter has 

 recently examined the type of Pemphigaspis bullata in the Ameri- 

 can Museum in New York, and is unable to connect it with what 

 we usually call Microdiscus. It therefore seems best to rehabili- 

 tate Eodiscus, as defined by Matthew, 7 to include a part, at 

 least, of the species now known as Microdiscus. Eodiscus 

 schuchcrti, Matthew, from the Lower Cambrian of Trov. N.Y., 

 thus becomes the type. The name Eodiscus was first used in 

 manuscript by Professor Hart, and mentioned by Walcott, 8 



:; Bull. Geol. Soc. France, ser. 2, vol. 18, p. 280, 1861. 



4 Bull. U.S. Geol. Survey, No. 30, p. 152, 1886. 



5 Paleontographical Society, vol. 61, p. 30, 1907. 



6 16th Ann. Rept. X.Y. State Cab. Nat. Hist., p. 221, 1863. 



7 American Geologist, vol. 18, 1896. 



s U. S. Geol. Servey, Bull. Xo. 10, p. 24, 1882. 



