io6 



HA RD WICKE'S S CIENCE- G OSS IP. 



height. A word about it in other lands may perhaps 

 be interesting. Miss Gordon dimming says : "Love- 

 liest of all are the delicate climbing ferns, the tender 

 leaves of which, some richly fringed with seed, hang 

 mid-air in long hair-like trails, or else, drooping in 

 festoons, climb from tree to tree, forming a perfect 

 net-work of loveliness. It is a most fairy-like 

 foliage, and people show their reverence for its 

 beauty by calling it the Wa-Kalon, or God's Fern."* 

 For superstitious reasons also the natives encourage 

 it to grow up their walls and door posts. Lygodium 

 japonicum has a pinnate frond ; in L. scandens, Sw., 

 the divisions are in pairs, broad at the base and 

 narrowing to a rounded apex, and of a more delicate 

 texture than the last, not nearly so common. L. 

 dichotomum, Sw., has fronds 8-IO inches long. 



Gen. III. Gleichenia, Sw. 



{Called in some places " Comb Ferny) 



Gleichenia dichotoma, Willd., is abundant, not only in 

 Hong-Kong where it is cut down for bedding for cattle, 

 but in the tropics all round the world. If it were not 

 for its trailing propensities, it might be compared to 

 the brake of our native land ; it is also not unlike 

 this fern in roughness of texture, although quite apart 

 in the position which by the formation of its seed it 

 holds in fern-classification. The spore-cases have no 

 covering, but are lightly set in a white flour-like 

 substance in loose groups of 2, 3, 4, or 5, under the 

 leaf. The fern is not very often met with in seed. 

 The arrangement of the long, stiff, pinnate leaves is 

 an easy distinguishing feature, as they grow in pairs, 

 or forked (hence the name di-chotoma, 2 cleft), each 

 fork resulting in another fork and so on, until the 

 long straggling branches form in some countries an 

 impenetrable jungle, too thick for a horse to break 

 through, and mounting 6, 8, or 10 feet high on 

 boughs of trees, low shrubs and underwood. It has 

 been called the "Comb Fern," as the leaves when 

 dry are stiff and like the teeth of a comb. 



( To be continued.) 



For some years past, attempts have been made 

 (without much success) to acclimatise the tea plant in 

 Italy. The Italian Minister of Agriculture has 

 determined to act upon the suggestions of Professor 

 Beccari, who has been investigating the subject, and 

 to procure some plants from the coldest provinces of 

 Japan, as well as some from the province of Novara 

 in Italy. The T/iea Sinensis has been grown to some 

 extent in the open in Italy, and Professor Beccari 

 thinks there is no reason why tea should not succeed 

 there, under proper management in procuring plants 

 and seeds and in the conditions under which they 

 are cultivated. 



* "At Home in Fiji," by Miss G. Gumming. 



CHAPTERS ON FOSSIL SHARKS AND 

 RAYS. 



By Arthur Smith Woodward, 

 of the British Museum (Natural History). 



IV. 



CESTRACIONTID/E. 



UNTIL quite recent years, the family of Cestra- 

 ciontidse was regarded as including all the 

 varied forms now grouped under the Orodontidse, 

 Psammodontidse, Copodontidce, Cochliodontidre, and 

 Petalodontida?, and thus its zoological and palaeonto- 

 logical signification has been considerably altered of 

 late. The most modern researches seem to show 

 that Acrodus and Strophodus are the only important 

 extinct genera that can be referred to it with certainty, 

 but Ptychodus is also placed here by most pakeonto- 

 ists, although it appears much more nearly allied 

 the Rays, judging from the little that is known 

 about the arrangement of its teeth. 



Reference has already been made to the dentition 

 of Cestracion, the only existing genus of this family, 

 in the account of the Cochliodonts (vol. xx. p. 270). 

 The diagram (fig. 71), however, will give a more cor- 

 rect idea of the aspect of the jaw : there is much more 

 variation in the dental forms in different parts of the 

 mouth than is to be observed among those sharks 

 with laniary teeth, such as the Carchariidae and 

 Lamnidre, and the hindermost are adapted for 

 crushing food, while those at the symphysis are dis- 

 tinctly conical and prehensile. Several rows are in 

 function at a time. It is a noteworthy fact, also, that 

 Cestracion has defensive weapon; in the form of 

 dorsal fin-spines, while the members of the families 

 just alluded to are destitute of these, their sharp 

 piercing teeth being a sufficiently formidable arma- 

 ture. Only four species of Cestracion are described 

 by Dr. Gvinther, in his British Museum Catalogue, 

 living off the coasts of Japan, Australia, California, 

 and the Galapagos Isles, and no undoubted fossil 

 remains of the genus have hitherto been recorded. 



As in the case of Hybodus, all the more perfect 

 specimens revealing the structural characters of 

 Acrodus have been obtained from the Lower Lias of 

 Lyme Regis. There have been discovered some 

 beautiful examples exhibiting the arrangement of the 

 dentition, others showing the two dorsal spines in 

 association with scattered teeth, and others indicating 

 that this genus possessed the four remarkable cephalic 

 spines so characteristic of nearly all, if not all, the 

 species of Hybodus. The most typical teeth of 

 Acrodus (fig. 73) are distinctly of the Cestraciont form, 

 and usually differ considerably from those occupying 

 similar positions in the mouth of Hybodus, being 

 quite flat or only slightly rounded, and ornamented 

 with very fine ridges and furrows radiating from a 

 more or less central longitudinal line ; the dentition 

 of this genus, too, varies more on different parts of 



