262 GEOLOGICAL MEMOIRS. 



the peripheral discs, which are seven in number in each ossicle, 

 and give its exterior surface the figure of a rosette. 



This specimen was obtained from the tertiary deposits near the 

 Rio Matanza, about twenty miles to the south of the city of 

 Buenos Ayres. 



3. Glyptodon reticulatus, Owen. 



This animal must have been a gigantic Armadillo, as large as 

 the G. clavipes, but differing in the sculpturing of the external 

 surface of the component ossicles, in which the peripheral raised 

 portions are of equal size with the central one, making the whole 

 exterior appear to be impressed by channels in the form of a net- 

 work. Hence the name by which the species is indicated. 



4. Glyptodon tuberculatus, Owen. 



This species is determined from a fragment of the carapace of 

 a gigantic extinct Armadillo, nearly equalling in thickness the 

 preceding specimen, but having the outer surface of the ossicles 

 divided into much more numerous elevations, separated by nar- 

 rower channels which unite to form a closer net-work : each emi- 

 nence or tubercle, of which there are between forty and fifty on 

 each ossicle, has a punctate surface. 



There is also a fragment of the carapace of the Glyptodon 

 tuberculatus, in which the component ossicles are square -shaped, 

 and, although the sutures are close on the smooth internal surface, 

 yet the tuberculated external surfaces of the ossicles are divided 

 by deep channels. The size and shape of the tubercles are so 

 similar to those in the foregoing specimen as to lead to the sus- 

 picion that the different form of the ossicles may have depended 

 on a modification of a particular part of the carapace. The ana- 

 logy, however, of the Glyptodon clavipes, in which species the 

 specimen in the Museum of the College affords the opportunity 

 of studying the extent of modification to which the constituent 

 ossicles are subject in the entire carapace, militates strongly against 

 the supposition that the various sculpturing exhibited in this and 

 the other specimens above described could have characterised par- 

 ticular parts of the carapace of the same species. 



This specimen was obtained from the tertiary deposits in the 

 Pampas of Buenos Ayres. 



III. On the Boulder Formation and on Diluvial Scratches in 

 Denmark and part of Sweden. By Gr. Forchhammer. 



[From Poggendorf's Annalen, bd. 58. s. 609.] 



The several formations of clay, sand, and boulders, all compre- 

 hended under the general term " Boulder formation," have lately 

 occupied the attention of geologists. For the study of the Scandi- 



