No. 1605. ON THREE SPECIES OF SHEA-TURTLES—HA Y. 187 
No. 29323 has only 11 (Plate VI, fig. 1). The sizes and the forms of 
the various neurals are extremely variable and it is often impossible 
to determine whether any particular bone belongs to the regular series 
or whether it is intercalated. 
The costal bones are, of course, the same in number as in the logger- 
head—8 pairs. On account of the large number of neurals, several 
of the costals articulate proximally with three of the former bones. 
In the smaller individuals there are extensive fontanels between the 
outer ends of the costal plates and the projecting ribs, quite as in the 
loggerhead. These disappear wholly or almost wholly in the largest 
individuals. 
The number of peripheral bones in the bastard-turtle varies be- 
tween 12 and 13 pairs. There may be 12 on one side and 13 on the 
other. Baur states that there are 13 peripherals, in one case 14; but 
it seems probable that there is some error here. In the small indi- 
vidual mentioned above, No. 29015, there are 12 peripherals on the 
right side, 13 on the left. The large specimen, No. 29323, has 12 on 
each side (Plate VI, fig. 1). A stuffed specimen, No. 29699, possesses 
14 marginal scutes on each side, from which it is inferred that there 
are 13 peripherals. When there are 12 peripherals the rib of the first 
costal bone enters a pit in the fourth peripheral, as in the loggerhead ; 
when there are 13 peripherals the rib enters a pit in the fifth. The 
extra peripheral, therefore, probably results from a division of the 
normal fourth. As in the loggerhead, all the peripherals succeeding 
the normal fourth have shallow pits for the rib-ends, except the tenth, 
the rib of the seventh and eighth costals having swung back so as to 
enter respectively the eleventh and twelfth peripherals. 
In the smaller specimens of the bastard-turtle, as in the loggerhead, 
none of the peripherals are suturally articulated to the outer ends 
of the costal plates. In the large individual, No. 29323 (Plate VI, 
figs. 1, 2), all the peripherals have come into close sutural contact 
with the outer ends of the costal plates, and the fontanels are closed 
up as completely as in most Emydide. Garman states that in his large 
specimens 8 or 10 of the posterior peripherals are joined by suture 
to the costals, making for the hinder half of the carapace nearly 
solid bone. On the other hand, the carapace of the loggerhead No. 
29013 is larger than any of the specimens just described and there 
are in it no unions between the costals and the peripherals, and con- 
siderable fontanels still occupy the borders of the carapace. It 
appears probable that the bastard-turtle does not reach the large size 
attained by the loggerhead in its old age. 
Mention has been made above of differences in the lateral periph- 
erals of the bastard-turtle and corresponding ones of the logger- 
head. It may be said that all the peripherals of the one species differ 
