The Galena and MaquoKeta Series. — Sardeson. 93 
mantle having penetrated it as in recent Bracliiopoda, be- 
cause, as I should guess, points of the mantle adhered to layer 
number one, number two growing around them. 3. On the 
ventral valve are the dental lamellae. They are impunctate, 
and are built from the beak forwards and upwards, the base 
only being imbedded in the punctate layer. Their apices are 
the teeth or articulating projections. 4. On the ventral valve 
between the "dental lamellae" is also a pedicle callist to the pos- 
terior surface of which was attached the pedicle, as the mus- 
cles were attached to the posterior surface of the other layer 
upon which the pedicle callist mainly rests. This part, too. 
grows at the anterior slope of its inner surface. It is situated 
really in the beak of the valve. On the dorsal valve are sim- 
ilar parts, viz. : 5. The septum, which is not always distin- 
guishable from the main punctate layer upon which it rests, 
fills the dorsal beak and exten.ds forward between the adduc- 
tor muscle scars. 6. Upon the posterior end of the septum, 
like a bent over part of the same, sits the impunctate cardinal 
process, which, as well known, formed on its posterior surface 
the attachment for four divaricator muscles, and which cor- 
respondingly is theoretically divisible into four coalesced 
parts. The median two parts extend beyond the other two, 
giving an outwardly tripartate division of the end of the 
process (fig. 8, pi. IV). The length of it varies directly with 
the convexity of the two valves, in individuals as well as be- 
tween varieties. 7. The erurae upon either side of the cardinal 
process vary likewise in length, are impunctate and coalesce 
with the cardinal process at their bases. 8. Small deltidial 
plates are rarely preserved. 
The place of attachment of muscles to the shell is marked 
by corresponding depressions, since under the attached ends 
of muscles no shell seems to have been deposited, and perhaps 
even reabsorption took place. As the animal grew the muscle 
attachments moved forward, leaving tracks that in part trailed 
over each other and that in turn became covered by processes 
of the shell advancing over them. There are always the four 
deep adductor muscle scars on the dorsal valve, of which the 
anterior pair are the larger. Of the eight muscle scars on the 
ventral valve the posterior or accessory divaricators are sel- 
dom to be seen, and the two adductors form one central scar. 
