96 
POPULAR SCIENCE REVIEW. 
There are no diaphragms, intertubular structure, or coenenchyma ; the 
spaces between the tubes are filled, in the fossils, with calcite, which also 
occupies the tubes. The course of the radial tubes is sometimes straight ; 
but usually they bend suddenly and repeatedly, and then pursue a straight 
course. They divide repeatedly. 
Of these curious and exceedingly problematical fossils, which he says are 
not crinoids, corals, sponges, or Foraminifera, Prof. Duncan proposes to make 
a new order, Syringosphseridae, and in it he distinguishes two genera : — 
Syringosphcera with eminences and pores on the surface, and Stoliczkaria 
without pores. 
Silurian Land-plants . — In September, 1877, Count Saporta described a 
fern from the slaty schists of Angers under the name of JEopteris Morierei. 
lie now (Comptes Rendus, 18 November, 1878) describes further evidence of 
the existence of ferns at the time of deposition of these rocks, referred to 
near the base of the Middle Silurian. His new material is the impression 
of the frond of a fern nearly 9 inches long, and about 3 inches in average 
width. It shows a slender rhachis bearing 7 pairs of leaflets, which are 
opposite or nearly opposite, of a rounded oval form, traversed by fine, 
divergent, flabellately dichotomous veins. These leaflets are sessile upon the 
rhachis, or nearly so. Beyond the seventh pair the apex of the frond is 
formed by a terminal leaflet, which appears to be round or reniform, folded 
upon itself, and perhaps composed of two portions partially soldered 
together. M. de Saporta names the species JEopteris Criei, after its discoverer, 
m! L. Ori6. 
Dwarf Crocodiles of Purbeck age. — Prof. Owen, in a paper read at the 
opening meeting of the Geological Society this session, described some 
diminutive crocodilian remains found in rocks of Purbeck age, which must 
have been contemporaneous with the well-known mammals of small size 
characteristic of these strata. In some slabs of “ feather-bed ” marl 
accompanying the Becklesian collection of Purbeck fossils in the British 
Museum, have been found in considerable abundance the remains of these 
dwarf crocodiles, to one of which Prof. Owen has given the name of Therio- 
suchus pu8sillu8. This crocodile appears to have been only about eighteen 
inches in length. It had its scales connected by the “ peg and groove ” 
arrangement, as in Goniopholis, with which genus it also agrees in many 
of its cranial characteristics, while in dentition it approaches more nearly to 
the Triassic Theriodonts than any other crocodiles. 
Lithology and the Classification of Crystalline Rocks. — Prof. Dana has just 
completed a memoir “ on some points in Lithology,” and the conclusions at 
which he arrives seem to be of such importance that we here reprint them. 
He says the principal points brought out in his paper are the following : — 
1. The necessities of the science of Geology constitute the most prominent 
motive for distinguishing kinds of rocks ; and they should determine to a 
large extent upon what characters distinctions should be based. 
2. In determining the rocks to be grouped as one in kind under a common 
name, near identity in the chemical and mineral composition of the chief 
constituents is the main point to be considered ; not near identity in their 
crystalline forms, for isomorphism presupposes diversity of composition. 
3. Distinction of kind should be based on difference in chemical and 
