NOVEJIBKR 1, 1889.] 



KNOWLEDGE. 



Hummel, this species assists its young to escape from the 

 egg case ; he introduced a female into a bottle containing 

 one of the cases ; she immediately seized it, and slit it open 

 with her jaws, and tore off the enveloping membranes of 

 the contained young. 



Besides house-cockroaches, we have in this country tield- 

 cockroaches, i.e. indigenous species that habitually live out 

 in the open and do not attach theniseh-es to mankmd. 

 They are smaller than I', (irirntalis, and may be found in 

 sandy places and amongst dead leaves and other vegetable 

 rubbish. They have sufficient superficial resemblance to 

 /'. (iriciitalis to be recognisable as coming into the same 

 category, although their colour is generally nuudi paler. 

 In addition to these, large numbers of species occur wild m 

 other countries ; but why just those particular species 

 mentioned above, and especially F. on'entalis itself, should 

 have become dependent upon the human race, while so 

 many others have either not attempted to do so, or have 

 not succeeded if they have attempted, is still shrouded in 

 mystery. The chief peculiarity by which oi-icnUdin is 

 distinguished from its fellows, viz. the apterous condition 

 of the female, seems rather as though it might militate 

 against its chances than favour them. 



THE FISH-LIZARDS OF THE SECONDARY 

 ROCKS. 



By R. Lydekker, B.A., Cantab. 



SO long ago as the year 1814, when a fine example of 

 a. lari^e skull (now in the ]5ritish Museum) was 

 figured by Sir Everard Home in the " Philosopliical 

 Transactions " of the Royal Society, the occurrence 

 in the so-called Lias of the Dorsetshire coast of 

 skeletons of huge and micouth reptiles, strangely unlike 

 any of their modern cousins, was well known. Five years 

 later the same writer described other specimens, and pro- 

 posed that these extinct Saurians should be known as the 

 Prntensaums, or Primeval Lizard. Now, strictly speaking, 

 this name, as the earliest, ought to have been adopted for 

 all time, but, unfortunately, the late Mr. Konig, some 

 time keeper of the Geological Department of the British 

 Museum, affixed to the specimens of these Saurians under 

 his charge the name of Iclithyosauyus, or Fish-Lizard ; and 

 this name was adopted in the year 1821 by the late Rev. 

 Mr. Conybeare, who, in conjunction with the late Dean 

 Buckland, of Oxford, did so much towards oui- knowledge 

 of the structure of these and other fossil Saurians. Tins 



quarrymen Lias, or Layers (the name being derived from 

 their banded and ribbon-like appearance) ; and before pro- 

 ceeding to discuss the structure of these creatures, a word 

 or two is advisable as to the geological position of the 

 formation. The Lias comprises a thick series of beds, 

 usually of a bluish colour, lying very low down in that 

 enormous series of rocks known as the Secondary system, 

 of which the Chalk is the topmost member, while the 

 middle part of the system is ibnned by the gi-eat series of 

 Oolites and their accompanying clays. The Secondary 

 system itself, it need hardly be said, lies upon the upper 

 part of the Primary system, as represented by the Coal 

 Measures ; while it is succeeded by the overlying deposits 

 of the Tertiary system. In regard to the upper parts of 

 the latter system, it is possible to make some more or less 

 vague approximation in terms of thousands of years as to 

 their real age, but in the Secondary period any such 

 approximation is totally impossible, and we can only 

 reckon the age of the various beds by geological periods, 

 as represented by the vertical thickness of overlying rock. 

 Now, since the Chalk may exceed 1,000 feet in tliickness, 

 and there are several deposits of equal bulk between this 

 and the Lias, some famt idea may be thereby conveyed of 

 the vast lapse of time by wliich we are separated from that 

 period when the mud of the Lias was deposited in the 

 shallow seas of what is now England. The Fish-Lizards 

 were, however, by no means confined to this remote Liassic 

 period, since they also occur not only in the miderlyuiL,' New 

 Red Sandstone, or Triassic series, which forms the very base 

 of the Secondary system, but likewise lived on through the 

 period of the Oohtes and Chalk, till they finally died out, 

 so far as we are aware, wuth the close of the Chalk period. 

 The Fish-Lizards are, therefore, characteristic of the 

 Secondary period, so that when we pick up one of the 

 joints of their backbones (of which more anon) we luiow 

 that it must have come from some part of that great 

 system, even though we find it embedded m the gravels 

 lying above the Tertiary system. One more important 

 point remains to be mentioned in connection with the beds 

 in which the remains of these Fish-Lizards occur ; and tliis 

 is, that they are all deposits formed by the sea, by which 

 we are led to conclude that these saurians were of marine 

 habits. Again, it may be observed that whereas in the 

 Lias the remains of the Fish-Lizards are usually found in 

 the condition of more or less nearly complete skeletons, 

 with every bone but little shifted from its natural position ; 

 in the overlying rocks the skeletons are generally more or 

 less dislocated and imperfect. Although the latter condi- 

 tion renders us unable to restore the complete skeleton of 

 these latter forms, yet it has hail the compensating 



l''i<:. 1. — Uitf;ATi,Y Ukuucki) Rkskiuaikin ov tiik Skuleton ok tiik Common Fisu-Lizakh of tiik Dohsktshiue Lias 



name has now become so thoroughly established — being, 

 in fact, almost an I'lnglish word — that, in spite of the 

 injustice to Sir I'lverard Home, it seems too late to 

 attempt its suppression. 



We have said that the Fish-Lizards havi' left tbcir 

 remains in those iieds of rock which ari> called b\ tlie 



advantage that we are able to handle and examine the 

 individual bones in a manner which is generally quite 

 impossible with the skeletons from the Lias, where the 

 bones are often distorted and tlatteued by pressure. 



We are now in a position to consider a few of the more 

 prominent featm-es in the structure of these primeval 



