Correspondence. 129 
cuts in text, July, 1893. By James Hall, assisted by John M. Clarke. 
"An unavoidable delay in the printing of the lithographic plates de- 
signed to accompany this volume renders it desirable to issue a part of 
the edition in the form of fascicles.*' The first fascicle treats of fifty- 
nine genera and subgenera, constituting the palaeozoic forms of the 
suborder Helicopegmata, or spire bearers. Sixteen of these genera are 
new, an increase of over thirty-five per cent. The work is illustrated by 
numerous wood cuts of the calcareous arm supports (here termed 
brae.hidium), from preparations by Mr. Clarke. Many good and detailed 
definitions and discussions of the interrelations of species and genera of 
this suborder are given, but a complete synopsis will require more space 
than this review admits. Only the more striking conclusions, therefore, 
will be noticed. 
In the forty pages here devoted to Spirifer, the plan adopted in the 
previous volume in treating of Ofthis is abandoned. The latter genus 
was divided into fourteen groups, each of which received a distinct 
subgeneric name, thus rendering it very easy to refer to any group. 
Spirifer, however, is divided into six primary sections; JZadiati, Lamel- 
losi, Aperturati, Ostiolati and Glabrati, all of these being again subdi- 
vided. Some of the secondary sections have a similar terminology, 
while other subsections are typified by characteristic species ; as Dis- 
junetus-type, Striatus4ype, etc. The number of sections and subsec- 
tions is thirty. For six of the subsections, the terms Delthyris, Reticu 
laria, Choristites, Martinia. Martiniop&is and Mentzelia, of authors are 
retained. It is not generally known, however, that the type species of 
Delthyris has a ventral septum, which proves this subgenus to beequa. 
to the section Lamellosi Septati, and not to the Fimbriati Unicispinei, 
as given in this fascicle. Mentzelia has been regarded as a subgenus of 
Spiriferina, and was so placed by Waagen in 1883 and by Bittner in 
1893, but whether this is correct is not now evident. 
The above classification of the Spirifers, which is based essentially 
upon surface characters, has been attempted a number of times, but no 
system has come into general use. It is admitted that Lingula, Orthis, 
Spirifer, and Bhynchonella, with their numerous species, are difficult to 
classify bi-, or trinomially, yet it would seem as though internal or de- 
velopmental characters rather than surface ornamentation might aid in 
the solution of the problem. This suggestion is not intended to convey 
the impression that the internal organization of Spirifer has not been 
studied, but it is believed that characters do exist in the many species 
of this genus, which can be used for subgeneric purposes. While 
knowledge of the interrelations which the species of Spirifer bear to one 
another has been greatly increased by this work, yet the former multi- 
nominal method of discussing them is not simplified by it. 
< 'yrtia, Dalman, is shown to differ from Spirifer only in having a high 
ventral area, with its delthyrium closed by a perforated deltidum. To 
the list of species should be added Spirifer metus, here referred to the 
"Pauciplicati" of the "Radiati" of Spirifer. 
Spiriferina is thought to have come through the lamellose-scptate 
