L30 The American Geologist. February, 1894 
spirifers. The same view was also held by the present writer in "A 
Classification of the Brachiopoda."* If this opinion is true, the pro- 
gression would not only be through an impunctate to a punctate stock, 
but would also include a change from an imperfect to a perfect loop, 
the imperfection of which is thought to have resulted in a partial ab- 
sorption of a complete ancestral loop. Cyrtina agrees with Spiriferina 
in having a perfect loop and a strongly punctate shell, while the other 
internal characters of Cyrtina might easily be modified into those of 
Spiriferina. Which of these views is the correct one can only be proved 
by an ontogenetic study of some species of Spiriferina. 
Metaplasia, gen. nov., is typified by Spirifer pyxidatus, Hall, to which 
should be added S. disparilis of the Corniferous, although it is referred 
to the septatelamellose spirifers in the present work. For another 
aberrant group of spirifers typified by the European S. cheiroptyx, 
the generic name Vemeuilia is proposed. 
"Davidson regarded Atrypa nitida Hall, as the type of Meristina, 
proposing Whitfieldia for M. maria, which is the original type of Me- 
ristina. Whitfieldia is therefore a direct synonym of Meristina, and 
for the latter genus, as understood by Davidson, the term Whitfieldella 
is here substituted. It is a question, however, whether the "unique 
loop'' and "peculiar fulness and close incurvation of the beaks" of Hin- 
della, Davidson, render it generically different from Whitfieldella, since 
other characters seem to he essentially alike in both forms. 
Hyattclla, gen. nov., is based upon Atrypa congesta Conrad ; while 
Dicamara, gen. nov., is founded upon Merista scalprum Roemer, a 
form occurring in the Eifel and having a "shoelifter'' plate for muscular 
attachment in both valves, while Merista herculea, its nearest generic 
relative, has but one, which is in the ventral valve. 
The type of Mcristella first recognized by Hall is Atrypa naviformis, 
a rare and nearly always imperfect shell. This species was later aban- 
doned by him for Merista kevis, the recognized type species of the 
genus. Conformity to the rules of nomenclature would not permit this 
had the genus been defined when the term Meristella was first used, 
but as this was not done, there can be no valid objection to founding 
the genus upon the second type. Charionella, Billings, is revived as a 
subgenus of Meristella. 
Camarospira, gen. nov.,hasfor its type Camarophoria eueharis Hall. 
It is supposed to be related to Mcristella and Merista, the loop, how- 
ever, being unknown. 
McCoy's abandoned athyroid genera Actinocohchus and Seminula, 
with Cliothyris, King, are emended and serve as subgenera of Athyris. 
While surface ornamentation is the most important distinction for their 
separation, there are internal differences as well. Athyris has a lamel- 
lose exterior (A. spiriferoides); in Cliothyris, the "lamellar expansions 
are divided almost, and sometimes quite, to their bases, into long, fiat 
spinules" {A. royssii); Actinoeonehus has an "extravagant development 
of the concentric lamellar expansions, which are striated by distant 
*Amerioan Geologist, vol. xi, 1893. pp. 141-107. 
