Hyde. — Camarophorella. 
PLATE 10. 
Ca ma rophorella m u ta bills . 
Fig. 51. Immature specimen viewed from the posterior end sliowing the 
structure of the jugum at an early stage. The position of the 
jugum is inverted with respect to the remainder of the drawings. 
Tlie saddle which becomes less distinct with growth is here con- 
spicuous, with a pronounced suture between it and the remainder 
of the jugum. The united portion of the accessory lamellae is 
much broader at the tip of the saddle than in the adult (compare 
with this figure 54 which is equally enlarged). The position of 
the secondary supporting plates in the beak of the pedicle valve 
between the inner surface of the valve and the spondylium is 
also .shown. X 8. 
Figs. 53, 54. Anterior and posterior views of the jugum of a small individual 
showing typical characters. X 8. 
Figs. 52, 55. Side views of the same specimen which show especially the 
relation of the expanded jilate on the anterior surface to the 
remainder of the jugum, and the features which suggest that it is 
a separate plate added subsequently. X 8. 
Fig. 56. View of the interior of an average-sized pedicle valve with its spondy- 
lium in which the brachidium is preserved entire except for the 
primary lamellae which are broken away and one of the accessory 
lamellae of the jugum. X 3. 
Merisia iypa from the Helderbergian, Cumberland. ^laryland. 
Figs. 57, 58, 59. Three views of pedicle valves of this species showing the 
variation in the "shoe-lifter." Figure 58 is the one which has 
suggested a possible line of evolution by which the spondylium of 
Camarophorella was produced. All after Hall and Clarke. '95, pi. 
42, figs. 9, 11, and 12 respectively. All natural size. 
Dicamara scalprum from Middle Devonian, Pelm, Germany. 
Fig. GO. "Ttio interior of a brachial valve; showing the 'shoe-lifter,' and the 
dividing median septum. Drawn from a gutta-percha impression 
which retains on the posterior margin a portion of the pedicle 
valve." This structure is fundamentallj' the same as that seer in 
"Camarophorella but differs considerably in the details. After 
Hall and Clarke. '95, pi. 42, fig. 15. 
