July 1, 189/5.] 



KNOWLEDGE. 



151 



sentativea of which are found in countries as remote from 

 one another as South Africa, New Zealand, Australia, 

 South and Central America, the West Indies, and 

 Sumatra. These animals have much the appearance of 

 caterpillars, having a jiair of simple antennae, and a 

 large number of short, conical, caterpillar-like feet 

 extending along the whole length of the under surface 

 of the body, and each terminating in a pair of hooked 

 claws. They breathe by tracheal tubes, after the manner 

 of insects, but instead of these tubes opening by a regular 

 series of apertures along each side of the body, their 

 openings are scattered in an irregular manner over its 

 whole surface. And it has been considered probable that 

 these animals are closely related to the ancestral stock of 

 insects, spiders and their allies, and myriopods. This 

 being so, it is evident that I'l lipntux must be an extremely 

 ancient typo, and there is a great probability that if their 

 remains were suitable for preservation we should find 

 evidence of their existence in some of the oldest rocks of 

 the northern hemisphere. It has, indeed, been assumed 

 from their present geographical distribution that these, as 

 well as many other types of animals, have always been 

 southern forms, and that their presence in the great southern 

 continents and islands indicates a former union of all the 

 lands of the southern hemisphere. That there wag a 

 south equatorial belt of land in Paleozoic times seems to be 

 pretty evident from certain peculiarities connected with 

 the Carboniferous flowers of the northern and southern 

 hemispheres, and it is, therefore, possible that in the case 

 of I'lripiitus such an explanation may be the true one. 

 Since, however, paheontology teaches us that many ancient 

 types have migrated from their original northern home to 

 find a refuge in the remote parts of the southern continents 

 and islands, it seems more probable that such has also 

 been the case with Peripatus. And if we can show that 

 ttiis has been the case with the scorpions, which now attain 

 tlieir maximum development in the more southern portions 

 of the globe, the argument will be strengthened in the case 

 of Peripatus. 



Probably most of my readers are fairly well acquainted 

 with the external appearance of scorpions, but, for those 

 who are not, the publishers have reproduced two very 

 beautiful photographs of a large African species, kindly sent 

 me by Dr. R. M. Howard, of Namaqualand, and locally 

 known as the sand-scorpion. Belonging to the great group 

 of Arachnida, which includes the spiders, the scorpions are 

 especially distinguished by their compressed bodies, and by 

 thesharp separation of theeephalo-thorax from tlieabdomen, 

 the latter consisting of seven segments, and being followed 

 by six narrower segments, collectively forming the post- 

 abdomen, the last of which is specially modified into the 

 so-called sting. The cephalo-thorax or fore part of the 

 body is covered by a shield-like carapace, upon the upper 

 surface of which are carried a variable number of simple 

 eyes, one pair of which is larger than the others, and is 

 placed dorsally, while the smaller ones are marginal. The 

 first pair of appendages are modified into short nipping 

 claws, while the maxillary palpi are greatly enlarged to 

 form the huge pair of pincers carried on each side of the 

 head ; aud the four pairs of walking legs are supported by 

 the first four segments of the thorax. It is important to 

 add that by means of pulmonary sacks opening by four 

 pairs of apertures on the sides of the abdomen, scorpions 

 breathe air, and it is accordingly only in rocka of fresh- 

 water origin, or such as were deposited near the shore 

 that their remains are likely to be preserved. 



According to the most recent classification, existing 

 scorpions are divided into four families, of which the first 

 two are again subdivided into several families. \n im- 



portant feature In this classification are the so-called 

 " pedal spurs," which are found upon the articular mem- 

 brane connecting the foot, a terminal segment of the legs, 

 with the segment that precedes it. According to Mr. 

 E. I. Pocock, the Scorpionidie, or typical scorpions, have 

 only one such spur, whereas two are present in the other 

 three families. It will, however, be quite unnecessary to 

 further consider the classification of the group in this place ; 

 but it is important to notice that one of the sub-families 

 of the ScorpionidcF is confined to Africa south of the 

 Sahara, and the Indian and Malayan countries ; while 

 another has representatives not only in those regions, but 

 also in northern Sovith America and Australia. At the 

 present day, indeed, scorpions are found in Europe only 

 in the more southern countries, where the majority of the 

 species are of comparatively small size ; and it is in the 

 tropical and sub-tropical regions of the globe that the 

 group attains its maximum development, the largest forms 

 being, we believe, South American and South African. 

 No scorpions are found in high northern latitudes, although 

 they range as far south as Patagonia, and none are known 

 from New Zealand. The species here figured belongs to 

 the typical sub-family of the ScvrpionldtE, which is confined 

 to the Ethiopian and Oriental regions.* 



According to the researches of Dr. Scudder, the modern 

 scorpions agree with one another in that the median dorsal 

 eye-tubercles are, as a rule, far removed from the front 

 margin of the cephalo-thorax, and thus placed behind the 

 lateral eyes. Apparently the only fossil scorpions agreeing 

 with this group that have been hitherto discovered occur 

 preserved in amber of late Tertiary age ; scorpions being 

 quite unknown in lower Tertiary or Secondary rocks. 

 Needless to say that this is not owing to their non-existence 

 in these epochs, but is due either to such rocks being 

 unsuited to the preservation of their remains, or having 

 been deposited far out to sea. 



When, however, we reach the Paleozoic coal-measures, 

 which are mainly of fresh-water origin, and, therefore, just 

 where we should expect to find such creatures, remains of 

 scorpions have been met with both in Europe and North 

 America, some of the species attaining very considerable 

 dimensions. Both in these Carboniferous scorpions, and 

 also in certain still older ones from the Silurian rocks, the 

 eye-tubercles are placed either on the actual front margin 

 of the cephalo-thorax, or only a short distance behind it ; 

 and these forms are thus regarded as forming a group apart 

 from the modern scorpions. In the Carboniferous genus 

 Cydiiphthahnus, the median eye-tubercles are immense, and 

 occupy almost the entire front half of the cephalo-thorax ; 

 the lateral eyes forming a semicircle behind and to the 

 sides of the larger ones. The maxiUary palpi form pincers 

 proportionally as large as in the modern forms, while the 

 legs have similar double claws. The genus Eoscorpiiis, 

 which is likewise common to the Carboniferous rocks of 

 both halves of the northern hemisphere, has all the 

 general features of the preceding, with the exception that 

 the arrangement of the eyes is different ; while Proscorpiits, 

 of the upper Silurian rocks of North America, is also of the 

 same general type. With Palmophonus of the Silurian of 

 Scotland and Gotland, we reach, however, a more primi- 

 tive type, in which the walking-legs gradually taper to thin 

 extremities, which terminate in simple claws or points, 

 although the palpi still form large pincers. 



Such is the palfeontological history of scorpions ; and a 

 remarkable history it is, seeing that most of the 



very 



* Mr. Pocock writes me that he believes the specimen to be 

 Opisthopthalmu.s pirlKpes:. The total length of the specimen in the 

 original photograph, which is natural size, is just over live inches. 



