SCIENTIFIC SUMMARY. 
181 
probability, this single body represents the single occipital condyle of the 
Reptilian skull , a part which remains cartilaginous in the Lizard long after 
the basioccipital is ossified, and is a distinct element. The structure of 
Cricotus shows that it is a connate intercentrum. Prof. Cope says : — ( We 
have now removed the last difficulty in the way of the proposition that 
the Reptilia are derivations of the Batrachia, viz., the difference in the 
cranio-vertebral articulation. But the former have not been derived from the 
Labyrinthodontia, as has been suggested, nor from the Ganocephala, but 
from the Embolomera, as I call the new order or sub-order. The order of 
Reptiles, which stands next to it, is, of course, the Theromorpha, which pre- 
sents so many Batrachian characters, including intercentra.’ The genus 
Diplovertobron , described by Fritsch from the Permian gas-coal of Bohemia, 
is believed by Cope to belong to the same group as Cricotus. 
Geology of the Cape Verde Islands. — Dr. C. Dolter gives a general account 
of the geology of the Cape Verde Islands in a letter to Prof. Von Hauer 
( Verhandl. k. k. geol. Reichsanst. 15 February, 1881). He says the group of 
of islands, consisting of two separate clusters, is of volcanic origin ; but in 
places there are also sedimentary rocks, especially limestone, as on the 
islands of Mayo and Bravao, which, with Santiago and the still active volcano 
Fogo, form the southern cluster. The unfossiliferous, dense, reddish limestones 
of Mayo, greatly remind one of the marbles of Trent. It would be difficult 
to determine their age, and for this purpose a study of the formations on the 
African continent would be necessary. The island of Santiago, the largest 
of the Archipelago, represents the remains of a very large volcano, of which 
the crater is still partially preserved in the Pico d’ Antonio, a peak of 2450 
metres in height. The great crater of the Pico d’Antonio has formed 
the whole island, and furnished an enormous number of lava - streams, 
separated by strata of tuff and rapilli. Veins are rare, and of subordinate 
importance. In the vicinity of the centre of eruption tuffs and breccias pre- 
dominate. Besides this great volcano, there are on the margins a dozen of 
smaller, secondary ones, from 200 to 400 metres in height. The products of 
the volcano are rocks which maybe characterized as andesites, olivine-basalts, 
and phonoliths, although, of course, their precise composition can only be 
ascertained by careful examination. As inclusions in the volcanic rocks, 
there are lumps of limestone converted into marble, and containing materials 
like serpentime and chlorite, and also phyllite, mica-schist, diorite, diabase, &c. 
The marbles are the most interesting of these, as such contact formations 
have hitherto rarely been observed in recent volcanoes. 
Of the northern group Dr. Dolter has only examined the volcano of San 
Vicenti, a great volcano the former crater of which forms the harbour of 
the island. It consists chiefly of lava-streams, which fall towards the sea 
uniformly at a gentle inclination. Between them are masses of tuff of sub- 
ordinate importance, with numerous veins. The margin of the crater has an 
elevation of about 1200 metres. In the midst of the crater Dr. Dolter found, 
to his great surprise, masses of dioritic and diabase-like rocks from two to 
three kilometres in length and breadth, some of them resembling hypersthe- 
nite; they were penetrated by veins of basalt and andesite, the rocks 
forming the volcano, and overtopped by lava-streams. Dr. Dolter thinks it 
probable that in these we have masses of the ancient continent, the existence 
