56 General Notes. 
Australia, a member of the Pleurodira. Mr. Boulenger bases his 
opinion upon the examination of a nearly perfect skull with the two 
cervical vertebree attached. The structure of the alveolar surface 
of the skull indicates an herbivorous animal ; the ungual phalanges 
and the curious sheathed tail a terrestrial one. This sheathed tail, 
with its opisthoccelous centra, is unique among the Pleurodira, 
and points toa distinct family. The ilium shows a surface for 
attachment to a sacral. 
The Pleurodiran characters are—the broad pterygoids, with outer 
palatal borders forming wing-like expansions ; the tympanic cavity 
completely surrounded by the bony roof; the articulation of the 
mandible by a condyle fitting into an articular concavity of the 
quadrate, and the form of the cervical vertebree. 
GEOLOGY OF THE SoLomon IsLanps.—Mr. H. B. Guppy has 
recently published a work upon the Solomon Islands, divided equally 
tween the volcanic and calcareous members of the group. The 
volcanic islands fall into two classes—the first comparatively modern 
and mainly composed of little-altered augite sandstones, andesitic 
pitchstones, tuffe and agglomerates; the second, composed partly of 
the above rocks, but in part of much more ancient crystalline masses, 
consisting chiefly of altered dolerites, quartz-diorites and porphyies 
and serpentines. 7 
he coral rocks of the Solomon Islands are divided by Mr. Guppy 
into: (1) True coral limestones; (2) Coral limestones which have 
the composition of the coral muds or sands now forming near coral 
reefs; (3) Rocks having the composition of volcanic mud and 
pteropod ooze ; (4) Foraminiferal limestones; (5) Rock resembling 
a consolidated deep-sea clay (red clay). The two last classes were 
evidently deposited at depths of not much less than two thousand 
fathoms in an ocean far from continental land ; and this is the first 
proof of their existence above sea-level. 
Mr. Guppy draws the following inferences: (1) That these up- 
raised reef-masses, whether atoll, barrier reef or fringing reef, were 
formed in a region of elevation ; (2) That such upraised reefs are of 
moderate thickness, their vertical measurement not exceeding the 
usual limit of the reef-coral zone; (3) That these upraised reef- 
masses, in the majority of islands, rest on a partially consolidated 
deposit which possesses the characters of the “ volcanic muds” that 
were found, during the Challenger Expedition, to be at present 
forming around volcanic islands; (4) That this deposit envelopes 
anciently-submerged volcanic peats. The author says: “ I never 
found one (raised reef) that exhibited a greater thickness of coral 
limestone than one hundred and fifty feet, or, at the outside, two 
hundred feet.” 
GEOLOGICAL SURVEY OF ARKANSAS.—From a small pamphlet 
—Annual Report of the State Geologist of Arkansas for 1887— 
