565.7 42 [January 



IV 



Dipeltis, a Fossil Insect? 



THE figures of the genus Dipeltis which accompany Mr Bernard's 

 interesting article in the last number of Natural Science are 

 very suggestive. According to Mr Schuchert, they represent fossil 

 Apodidae. To Mr Bernard himself, who adopts Mr Schuchert's 

 view, Dipeltis looks remarkably like a cross between an Apus and a 

 trilobite ; while the first thought that occurs to an entomologist is — 

 how wonderfully like insects these ancient Apodidae must have been. 

 But the entomologist need not stop at this suggestion. He may 

 venture to go further and ask — What greater reason is there for 

 regarding Dipeltis as a fossil crustacean than for considering it to be 

 a fossil insect ? 



The structure of Dipeltis, so far as it can be made out from the 

 figures and from Mr Schuchert's description, agrees well in all essen- 

 tial respects with that of an insect ; the three large anterior seg- 

 ments are easily explained as the three divisions of the thorax ; this 

 is followed by an abdomen, consisting in one species of seven, in the 

 other of ten segments, just about the number we should expect to 

 find ; and in one species at least the abdomen bears at the extremity 

 a pair of jointed cerci, not unlike the cerci met with in many 

 differrent insects. 



Unless there be some good and sufficient reason, not to be found 

 stated in Mr Schuchert's paper, it is hard to understand why all 

 these insect-characteristics have been entirely left out of account in 

 discussing the zoological position of the genus. Mr Bernard has 

 personally told me that his chief ground of objection to considering 

 Dipeltis as an insect is in the presence and position of the four 

 eyes. That would be a fatal objection, I admit, if Mr Schuchert's 

 interpretation were proved to be correct. But as matters now stand 

 it has no force whatever. There is no necessity to go beyond the 

 actual facts of the case. What has to be explained is the presence, 

 not of eyes and ocelli, but of " two faintly preserved spots " and " two 

 small shallow pits." Assuming that the so-called head-shield of 

 Dipeltis is in reality the pronotum of an insect, it requires no effort 

 of the imagination to account satisfactorily for the presence of these 

 pits and spots. It is not at all exceptional to meet with pits and 

 spots and tubercles on the pronotum of insects, nor would it, per- 

 haps, be very difficult to adduce examples in which the pits and 

 spots approximate closely in number and position to the " eyes " of 

 Dipeltis diplodiseus. Dr Woodward has described and figured a 



