On Fossil Arthropoih in the British Museum. 273 



rarispinus, plate 23, fig. 1, area I. This is an external sand- 

 stone mold of the ventral side seen from above, and is there- 

 fore reversed, as is your specimen of P holidocidaris anceps 

 seen from within. 



" I found in the great preponderance of cases in Palaeozoic 

 Echini that odd-numbered columns, while starting in the 

 centre, passed upwards to the left of the centre. On the other 

 hand, even-numbered columns usually start on the rigiit of 

 tlie centre and maintain that position throughout their extent. 

 Such being the case, I feel that such is the probable course in 

 any given specimen until it proves itself exceptional. 



" This internal and external view business and molds of 

 exterior and interior seen in reverse are the most confusing 

 things to keep true orientation straight in that I ever 

 tackled." 



XXX YI. — Fossil Arthropods in the British Museum. — I. 

 By T. D. A. COCKERELL, University of Colorado. 



The British Eocene insects hitherto described consist of three 

 species of Coleoptera, one of Isoptera, and one of Odonata. 

 The two latter, published in recent years, are in the British 

 Museum. Dr. F. A. Bather has kindly transmitted to me 

 the'undescribed Eocene material belonging to the Museum, 

 and included with it I find the type-specimens of two of the 

 already-named Coleoptera. These were figured by Wt'Stwood 

 in 1854, without names ; in 1856 names were supplied by 

 Giebel. 



In the present paper I complete the account of the Eocene 

 material, aside from the Coleoptera, which will be discussed 

 separately. Six species are described, more than doubling 

 the list, and adding three orders. The ants are the olde.st 

 Old-World species. 'I'he Fulgorid represents a tyjie of 

 broad-winged moth-like llomoptera, well developed to-day in 

 the Oriental region, but especially prominent in the Eocene 

 fauna of the Rocky Mountains, as I shall show in a paper 

 now awaiting publication. !So far as can be seen, the English 

 insect belongs to one of the American genera. The most 

 remarkable find, however, is a large wing belonging to the 

 Mesozoic family Pseudosiricidae. Its discovery is almost as 

 startling as that of a Tertiary dinosaur; but after careful 

 study I cannot separate the species from the Meso/oic group, 

 and, indeed, it is very close to the genus Formicium. 



Ann. dk Mug. N. Ilisl. Scr. 9. Vol. v. VJ 



