May 7, 1891] 



NATURE 



belonging to the same ordinal group (Chilopoda). The 

 essays respectively commencing on pp. 195 and 247 of the 

 first volume give the full history of the specimens on 

 which the author founded the orders Protosyngnatha and 

 Archipolypoda. The former group is represented only by 

 a single specimen from the Carboniferous of Illinois, 

 described as Palceocampaj this curious creature being 

 of small size, and in its short body, with pencils of 

 bristles on the back, presenting a superficial resemblance 

 to the well-known larva of the tiger-moth. Of more 

 interest are the Archipolypoda, confined in America to 

 the Carboniferous and Permian, although represented in 

 the " Old Red " of Scotland. A restoration in Plate 

 \ ii. A, of one of the largest of these creatures {Acatit/ier- 

 pcsies) gives an excellent idea of their extraordinary 

 appearance ; the animal being represented as emerging 

 from the water and ascending the stem of a Lepidoden- 

 dron. The figured species attained a length of about 

 one foot ; its amphibious habits being inferred from the 

 presence of lateral apertures presumed to be branchial. 

 The Archipolypoda agree with the Diplopoda, or Mille- 

 pedes (and thereby differ from the Chilopoda), in having 

 two ventral plates, each carrying a pair of limbs, to every 

 dorsal plate, but differ in that each dorsal plate occupies 

 at most only two-thirds, instead of nearly the whole of 

 the circumference of the body. The larger species, like 

 the figured one, were further distinguished by carrying 

 rows of long spines on the dorsal plates. The smaller 

 forms originally discovered by Sir J. W. Dawson in the 

 Sigillarian stems of Nova Scotia, which were doubtless 

 of purely terrestrial habits, and have been described as 

 Xylobius and Archiiilus, appear to indicate a distinct 

 group of this order approximating to the modern 

 Millepedes. 



As an instance of the danger of drawing inferences in 

 palaeontology from negative evidence, we may quote a 

 sentence from p. 196 of the first volume, where the author 

 states that " The Diplopoda are universally considered 

 the lower of the two in their organization, and it is there- 

 fore not surprising to find that no Chilopoda have been 

 found in rocks older than the Tertiary series, while 

 Myriopods with two pairs of legs corresponding to 

 each dorsal plate range back through the entire 

 series of rocks to the Coal-measures." This inference 

 is, of course, completely traversed by the above-men- 

 tioned discovery of Carboniferous Chilopoda ; and it 

 may be suggested whether the presumed coalescence of 

 two dorsal segments in the Diplopoda and Archipolypoda 



>>t a character in advance of the Chilopoda. 

 le only essay devoted to Arachnids in the first 

 me is the one commencing on p. 419, which was 

 nally published for the first time in September 1890. 

 essay treats of the Palaeozoic order Anthracomarti, 

 c^.^v^ of that division of the Pedipalpi known as the 

 Phrynidea ; the Scorpions being reserved for a future 

 occasion. The Arachnids differ from both the insects 

 and Myriopods in being represented by an existing order 

 (Scorpions) as far back as the Silurian. Indeed, the 

 only extinct order of the class is the Anthracomarti, 

 which is confined to the Carboniferous, and is regarded 

 as having some points of connection with the Adelarthro- 

 somata, as represented by the Phalangidae (" Harvest- 

 men"), and others with the Pedipalpi, the relationship 

 NO. I 123, VOL. 44] 



being on the whole nearer to the latter. They are charac- 

 terized by their somewhat depressed bodies, in which the 

 abdomen is distinct from the cephalothorax, and consists 

 of a single mass composed of from four to nine distinct 

 joints ; while the palpi are short, and do not terminate 

 in pincers or claws. With the possible exception of the 

 Scorpions, these appear to have been the most abundant 

 of the Carboniferous Arachnids, and were represented by 

 a number of genera ; those described in the essay before 

 us being arranged in two families and six genera. In 

 the Phrynidean section of the Pedipalpi, containing the 

 Spider-Scorpions, Mr. Scudder describes a new Car- 

 boniferous genus, Grccophonus, besides giving further 

 characters of a previously-described species oi Geralinura, 

 v.hose nearest living ally is Thelyphomes, of the tropical 

 regions of Asia, America, and Australia. 



Passing to the second volume, on the Tertiary insects, 

 of which only a very brief notice can be given, we may 

 touch upon a few points mentioned by the author in the 

 introduction. One of the most noteworthy circumstances 

 to which he refers is the extraordinary profusion in which 

 insect remains have been preserved in some of the 

 Tertiary lake-basins of North America, this being espe- 

 cially the case with the Florissant basin of Colorado, 

 belonging to the Oligocene epoch. Not less remarkable 

 is the fact that in " hardly a single instance has the same 

 species been found at two distinct localities"; and this 

 not only when the localities are separated by hundreds of 

 miles, but even when they are comparatively near. The 

 author considers that this peculiarity may be explained 

 by the absence of exact synchronism between any of 

 the insectiferous beds, and he is thus led to infer that 

 insects will probably afford very valuable aid in deter- 

 mining geological horizons, the modification of species 

 having progressed much more rapidly than is the case 

 with plants. 



Another point to which attention is directed relates to 

 the extraordinary number of forms known only by a 

 single specimen ; the author stating that, in beds whence 

 thousands of insects have been obtained, every third or 

 fourth specimen will prove to be a new form. The in- 

 terest of these investigations is enhanced by the discovery 

 that a considerable proportion of the Tertiary insects must 

 be referred to extinct genera ; the author considering that 

 a large number of the species he has placed in existing 

 genera will eventually have to be removed to new ones. 

 We trust, however, that Mr. Scudder will not burden the 

 science with more new terms than are absolutely essen- 

 tial ; more especially since, if he favours us with a new 

 edition of his " Nomenclator," he will have the additional 

 labour of recording them a second time. 



Following the introduction there is a chapter devoted 

 to the American localities where fossil Tertiary insects 

 are most abundantly found. In addition to the Florissant 

 basin of Colorado, there are deposits of approximately 

 the same age on the White River in Colorado and Utah, as 

 well as on the Green River in Wyoming. Less productive 

 spots include a town in Wyoming, rejoicing in the appro- 

 priate name of " Fossil," as well as various places in 

 British Columbia, Ontario, and Pennsylvania. There are 

 also a certain number of insects— mostly Coleoptera — 

 from Pleistocene or recent bone-caves and other super- 

 ficial deposits. 



