HARDWICKE'S SCIENCE-GOSSIP. 



35 



IMarsh's figures, showing that in recent birds the 

 •cerebral hemispheres have largely increased, while 

 ithe prominence of the olfactory and optic lobes, a 

 marked reptilian character, is greatly diminished. 



The structure of the Odontornithes throws con- 

 siderable light on the origin of birds and the genea- 

 logy of the race. Their history makes it evident 

 that two types, each differing widely from the other, 

 were contemporaries in an aquatic paradise of the 

 tropical ocean of the chalk epoch in Western America. 

 In one the primitive form of biconcave vertebra?, 

 clearly pointing to an ancestry even lower than the 

 reptiles, was associated with a skeleton resembling 

 •that of existing keel-breasted birds ; the other ex- 

 hibited peculiarities now found only among the 

 scanty survivors of the Ratite race — the flat-breasted 

 •ostriches, and their congeners, the most reptilian of 

 all living birds. Both these types were united by 

 the possession of teeth, which separates them from 

 all existing species, and it is possible that some other 

 •of their contemporaries were alike distinguished 

 by this peculiarity. For no less than nine avian 

 genera, represented by twenty species, are now 

 known to have existed in America during the 

 deposition of the chalk. All these, however. Pro- 

 fessor Marsh points out, were aquatic species, and 

 therefore peculiarly liable to be preserved in marine 

 ■deposits. 



The solitaty Archreopteryx of the European Jurassic 

 as the only known example of a Mesozoic land bird. (?) 

 A second specimen of this remarkable genus was dis- 

 covered in the same locality, by the son of the 

 fortunate finder of the first example — that now in the 

 British iVIuseum. This was purchased by Dr. Siemens, 

 of Berlin, for 20,000 marks (800/.), with a view to 

 its retention in the Fatherland, it was subsequently 

 bought by the Prussian Government for 18,000 marks, 

 .and is now in the possession of the. Unirersity of 

 Berlin. According to Karl Vogt, the hind limbs 

 only are avian, the other portions of the skeleton 

 being entirely reptilian. The breastbone is keelless, 

 .and there is no " merry-thought." From the osseous 

 structure of the fore limbs, terminating in three free 

 fin"-ers, it would be. impossible to describe the animal 

 as a bird, had no feathers been preserved. These 

 are, however, well developed on the neck, legs, and 

 ^-wings, and the presence, even of the underlying 

 down, is indicated. Hence, it was concluded that 

 the body was naked, as no feathers occur on its 

 surface. Was it moulting at the time of its entomb- 

 ment in the fine mud of the Solenhofen seas ? But 

 Professor Owen has suggested that the absence of 

 the soft body feathers is not absolute proof of their 

 non-existence, as it is just on that portion of the body, 

 they would first become detached from the carcase 

 as it floated on the water ; the stronger roots of wing 

 and tail plumes retaining them longer in position, 

 and thus protecting the underlying down. But 

 •whether half naked, or wholly feather-clad, the pre- 



servation of the wing and tail coverings proves that 

 those usual accompaniments to hot blood and an 

 aerial existence were fully developed at an early 

 Mesozoic age. Two minute teeth have been detected 

 in the upper jaw of Archceopteryx, and Professor 

 Marsh believes that eventually this genus will be 

 found to possess the biconcave form of vertebrae. 



Such is the complex structure of this feathered 

 lizard, or reptilian bird, capable of quadrupedal 

 locomotion. Its occurrence in the Jurassic, and that 

 of the aquatic ostrich, Hesperornis, and tlie fish-like 

 Ichthyornis in the Cretaceous epoch, Professor Marsh 

 holds to be proof of the extreme antiquity of the 

 race of birds thus early represented by three such 

 differentiated types. He further suggests that the 

 ancestral forms of primeval arboreal birds — feathered 

 limbed, and even more reptihan in structure — may 

 yet be discovered in America in some of the old land 

 areas of Triassic, or possibly of Permian age. Who, 

 remembering the twenty species of cretaceous birds, 

 which, utterly unknown a few years back, now form 

 the subject of his splendid memoir, shall venture to 

 define that anticipation as too sanguine ? 



CHAPTERS ON BRITISH DRAGON-FLIES. 



No. I. 



By E. B. Kemp-Welch. 



WHEN first commencing, some years since, the 

 study of these insects, I found considerable 

 difficulty in identifying my captures, as there 

 appeared to be no work obtainable treating of the 

 British species, nor, I believe, has this want been 

 supplied up to the present time. Latterly some queries 

 have appeared in Science-Gossip as to names of 

 specimens taken, and it occurs to me that a short 

 description of the various species inhabiting Britain 

 may, at any rate, be of some assistance to beginners 

 in the study of these insects. 



The system of classification followed is that of 

 Dr. Hagen, whose descriptions of species I propose 

 also to adopt in the case of species not in my collec- 

 tion, or of which I have no figures. Before com- 

 mencing I will give a itw diagrams, 2. reference 

 to which, from time to time, will assist beginners 

 in understanding the technical terms used to dis- 

 tinguish the various parts. 



British dragon-flies are easily divided into two 

 groups, distinguished as follows : — 



FIRST GROUP. 



Wings dissimilar in shape ; the hinder wings being dilated at 

 the base. 



Eyes more or less contiguous. 



FAMILIES. 



Libellidida: 'i l^^^.^j. ];„ ^^ labium, smaller than the palpi. 

 Corduhidcr- ) 



GomphUfii; ) Lower lip, or labium, larger than the palpi. 

 Aischniacv j 



