UCTOBEK 1, 1894.] 



KNOWLEDGE 



223 



species obtained from the lower Eocene sand of Kyson, 

 in Suffolk, were at first supposed to pertain to a monkey. 



If the paliEontological riches of the United States have 

 helped in the elucidation of the true affinities of the 

 hyracothere, still more markedly is this the case with 

 regard to the much larger ungulate originally described 

 on the evidence of detached teeth from the London clay 

 under the name of Coriiiihodon, in allusion to the strongly 

 marked oblique crests surmounting their crowns. From 

 nearly complete skeletons discovered in America, we know 

 that the coryphodons, which were animals with somewhat 

 the proportions of a bear, although furnished with a 

 well-developed tail, differed from both the odd-toed and 

 even -toed ungulates in having five toes to each of the very 

 short and wide feet, and likewise in the structure of the 

 feet themselves. The molar teeth, too, as shown in figure 

 ( ' of the illustration, are likewise quite different from those 

 of any li\ing member of the order, and are remarkable for 

 the extreme shortness of their crowns. The nearest allies 

 of these animals were the uintatheres of North America, 

 distinguished by the presence of a large pair of tusks in 

 the upper jaw, ■ and thetwogroups collectively constitute 

 the order of short-footed ungulates. 



One remarkable palate of a mandible from the London 

 clay of Heme Bay, preserved in the museum at York, and 

 described under the name of Plati/charops, has given rise to 

 some amount of discussion as to its serial position. It has 

 been suggested, however, that it belongs to a peculiar 

 group of mammals from the North American Eocene, 

 which combine many of the characteristics of the ungulates, 

 carnivores, and rodents. Of the latter order there are but 

 small traces in the lower British Tertiaries ; but some 

 lower jaws from the Hordwell and Headon beds have been 

 referred to the genus Theridomij^, which is of common 

 occurrence in the corresponding continental strata, and 

 indicates an extinct family of the order. Whales are like- 

 wise rare, but from the Barton beds there has been 

 obtained a skull belonging to the peculiar group of 

 zeuglodonts, which are not improbably the ancestral types 

 whence the modern toothed whales have been evolved. 

 Unlike all existing members of the order, these extinct 

 cetaceans had double-fauged molar teeth, whose com- 

 pressed crowns had tlie edges surmounted by well-marked 

 serrations ; and, what is more remarkable, their bodies 

 appear to have been invested with a bony armour 

 comparable to that of crocodiles. 



The last of the Tertiary mammals that we have to 

 notice are opossums {liidelphya), remains of which have 

 been detected both in the HordweU beds and in the lower 

 Eocene sand of Kyson. It is almost superfluous to add 

 that opossums, which in Oligocene and Eocene times were 

 widely spread over Europe, are now confined to America, 

 where they attain their greatest development in that half 

 of the continent lymg to the south of the Isthmus of 

 Darien. The relegation of the originally European genus 

 to the New World is somewhat analogous to the banish- 

 ment of the nearest living allies of the British Jurassic 

 mammals to Australia, and is a well-marked instance of that 

 gradual disappearance of the lower types of mammalian 

 life from the western regions of the Old World, with the 

 development of higher forms, which seems to have been such 

 a characteristic feature in the evolution of the present 

 faunas of the globe. Since we have already discussed the 

 mammalian fauna of the Jurassic rocks of Britain in our 

 article on " The Oldest Mammals," we may be excused 

 from further reference to that part of our subject on the 

 present occasion. 



* See the figure in a previous article on " Tusks and their Uses." 



INSECT SECRETIONS.-VI. 



By E. A. Butler, B.A., B.Sc. 

 {Continued from page 198.) 



THE secretions formed by beetles of which we have 

 hitherto spoken are of use only to their fabricators, 

 but we have now to consider a family of beetles 

 whose products have for a long time been turned 

 to account by human kind, and made an important 

 article of commerce. This family is the Cantharida or 

 Mtdo'idcF, some of the best known members of which are 

 called blister beetles and oil beetles. The family is a very 

 extensive one, containing more than a thousand species 

 already described, which are world-wide in their distribu- 

 tion, though the majority have their home in tropical 

 regions. Of this vast company we have only a very small 

 sprinkling in Great Britain, a select group of nine species, 

 distributed amongst three genera. Several of the nine 

 are amongst our rarest insects, and not more than one or 

 two are common. However, this small company contains 

 the most useful insect of the whole family, the renowned 

 Spanish fly, or blister beetle, Li/tta or Cantharis rcsiccitoria. 

 Nothing more romantic than the life-history of the 

 insects belonging to this family can be found throughout 

 the whole range of insect life. It may be remembered 

 that we have given details of two species of Melo'ilce in 

 our articles on " Bee Parasites," viz., the common oil 

 beetle, and the beetle named Sitaris muralis (see Knowledge, 

 Vol. XV., p. 166). These may be taken as typical of the 

 group, and the general history of a Meloid may, therefore, 

 be summarized as follows : — The eggs are extremely 

 numerous, and on hatching produce very minute six-legged 

 creatures, which have not merely the usual pair of claws 

 at the end of each foot, but in addition a central pad, 

 which looks hke a third claw, whence these little beings 

 are often spoken of as " triungulines " (three-clawed). 

 They are also distinguished by possessing long bristles 

 at the end of their bodies. They are very active, and 

 their one business is to discover a suitable kind of 

 bee, to whose body they may cling, so that they may 

 be carried away by it. and obtain entrance into its nest. 

 Here the little adventurer devours the bee's egg, and then 

 becomes changed into a fat-bodied, short-legged creature, 

 utterly unlike the little triunguline that produced it. The 

 food of this clumsy larva — for larva still it is, notwith- 

 standing its change of form — is the store that has been 

 laid up by the bee for her own young. By the time this is 

 finished, the larva has lost its legs and become barrel-shaped. 

 But the cycle of changes is not yet complete ; other phases 

 have to be passed through before we arrive again at the 

 point from which we started. In the next stage it is a 

 six-legged grub again, similar to what preceded the legless 

 barrel. After this it changes to an ordinary chrysalis, 

 from which in due course the perfect beetle issues. 



The great peculiarity in this marvellous history is the 

 existence of two totally distinct types of larva, which 

 succeed one another in time, viz., the active, running 

 triunguline, which reminds us somewhat of the larva- of 

 those insects that have an incomplete metamorphosis, and 

 the crawhng caterpillar-like being, which is typical of the 

 larvffi of those insects whose metamorphosis is complete. 

 And here again there is a further complication, this form 

 appearing twice, and its two appearances being separated 

 from one another by an interval during which the creature 

 passes into a form resembling the barrel- shaped chrysalis 

 of a fly. Thus we seem to have in the total twice as 

 many stages as are usually to be met with in the develop- 

 ment of an insect. 



