J:iniinry — March 1SS5.I 



PSYCHE. 



240 



a ilivcrsity of stiiicture inconsistent with 

 a belief in our having reached the prim- 

 ordial forms of this phylum in our 

 retrograde search. 



When, in 1S5S, Bronn published his 

 prize essay on the distribution of fossils, 

 only two species of pretertiary arach- 

 nida were known as such, one from the 

 carboniferous and one from the Juras- 

 sic formation, and the knowledge of 

 tertiary forms was confined entirely to 

 the then recently published work of 

 Koch and Berendt on the species from 

 amber. Since then Menge has in- 

 creased somewhat our knowledge of the 

 amber fauna, and it includes to-da}' nine- 

 tenths or more of the known tertiary 

 species. But it is only within the last 

 fifteen j'ears that our knowledge of pre- 

 tertiary arachnida has been extended 

 beyond the description of two or three 

 species. The number is still exceedingly 

 few — between 20 and 30 species — but 

 it is being constantly extended, and the 

 abundance of arthropoda brought to 

 light in recent years in the carboniferous 

 deposits <jf AUier, Bohemia, Scotland 

 and Illinois leads us to expect an earl}' 

 and consitlerable extension of the list. 

 This expectation is strengthened by 

 Lindstroni's and Hunter's discoveries of 

 scorpions in the upper Silurian rocks ot 

 Gotland and Scotland. 



The forms that have been found fossil 

 in the earlier formations have proved, 

 as might be expected, to belong mostly 

 to those having a dense integument, 

 and in the two species believed to be 

 true araneae, the abdomen was proba- 

 bly provided with more or less densely 



chitinoLis dorsal plates. With these 

 two exceptions, and a single genus of 

 fiedlpalpi, all the paleozoic arachnida 

 ( onlv a single mesozoic form is 

 known) belong either to the scorpio- 

 iiidcs or to a peculiar group, the anthra- 

 comarti. This group is not found later, 

 and the single known species of me- 

 sozoic arachnida* is a true Aranca. The 

 paucity of remains of arachnida in 

 mesozoic strata is somewhat remark- 

 able. Besides the species mentioned 

 above, only one other has been indicated, 

 a species supposed to belong to the 

 araneae, from the English Has. 



Thanks to the amber deposits of Prus- 

 sia, we know iar more about the tertiary 

 history of arachnida than would be 

 possible if our sole reliance were on the 

 rocks, the latter furnishing us with only 

 about double the number of those occur- 

 ring in pretertiary deposits. In the 

 amber alone occur all the suborders of 

 aracluiida, excepting the pcdipalpi 

 and the already extinct a?iihracomarti, 

 as well as all the families of araneae 

 excepting one peculiar to the Jurassic ; 

 but in the tertiary rocks neither chelone- 

 t//i, scorpioncs nor opilioties have been 

 recognized ; of the pcdipalpi., a single 

 species is referred to by Serres from the 

 niarnes of Aix, but too obscurely to 

 take account of it. 



Examining the araneae alone, which 

 are far better represented in the tertiaries 

 than are the other suborders, we find a 

 very large number of extinct genera. 

 In all, seventy-one are now known, 



* Palpipes or Phalangites, believed even by Thorell 

 lo be .in arachnid, has been shown by Seebach to be a 

 stomatopodous crustacean. 



