130 The American Geologist. Angust, 1896 
radially lined shells, without lunule, gaping in front, with beaks bent 
backward, the cliif being very long. The shells have the aspect of 
Hemicardium and were so termed by Barrande. Six species are de- 
scribed from the middle and upper Devonian. 
Prochasma, nov. Another group of Lunulicardium-iorvafi in which 
the outline is elongate, the anterior cleft in the valves transects the 
beak, is shorter and more oblique than in Chcenocardiola. The surface 
of the valves is generally without radial ornament. The 10 species de- 
scribed are from the upper Devonian. 
Family Conocardiidte. Conocardio2Jsis, nov. Introduced for a pingle 
species (C. lyelli dWrch. and de Vern. Middle Devonian) in which the 
posterior slope is carried out into a short open tube aud, on the anterior 
slope the valves gape. It is regarded a passage form from Lunuli- 
cardiiim to Conocardiuvi. 
Co)iocardium, Bronn. 13 species. 
In a chapter on the "Systematik " of these fospils, some interesting 
points are brought forward, those pertaining to the value of Neumayr's 
general divisions being suggestive. Neumayr proposed as one of his 
ordinal terms, PalEeoconchae, for a group of thin shelled, toothless 
species in which were included a number of familiep, the Cardiolidae, 
PraBcardiidffi, Lumulicai'diidae, Antipleuridge, etc., etc. These shells are 
highly developed in the Silurian and lower Devonian faunas of the 
Bohemian basin and Neumayr's observations were lar;:^ely derived from 
their occurrence there. They constitute a peculiarly interesting, if 
heterogeneous group and are all in need of closer study than their great 
delicacy of structure has yet permitted them to receive. They are 
abundantly represented in the lower upper Devonian of New York. 
Neumayr held this order to be primitive and the points of departure of 
those more highly differentiated. Numerous arguments have been 
brought forward against this view, the entire gi-oup being actually of 
comparatively late paleozoic age, undoubtedly occurring in some meas- 
ure in the upper Ordovician of certain localities, but nevertheless re- 
maining an emphatically Devonian association. The taxodonts are 
much more ancient and Jackson has demonstrated their primitive char- 
acter from a study of the mode of development in these shells. Though 
it is now difficult to understand the precise relation of these "jjala?o- 
conchs" to other recognized orders of the lamellibranchs, it would seem 
that the author more nearly approaches the truth in his suggestion that 
they are of an obstructed and reverted type. The name is here fo'*mally 
rejected, both on account of its being a misnomer and because of its 
incongruity as an ordinal term. In its place, to embrace three of its best 
known families, the Cardiolidfe, the Lunucardiidie and the Conocardii- 
diB, is introduced the new ordinal term CardioconchiB. 
Two closing chapters of this work are entitled "The geological distri- 
bution of the bivalves in the Rhenish Devonian and their significance 
in stratigraphy," and "The relations of the bivalve fauna to the facies 
development of the Rhenish Devonian." In the latter chapter many 
interesting facts pertaining to bathymetric distribution are brought out. 
one of which is that the palasoconchs are largely if not exclusively deep 
sea forms. • J. m. c. 
