3S6 Summary on the Patagonian pakt n. 



200 feet in height, and are composed of fine sandstones, 

 often in curvilinear layers, including hard concretions 

 of calcareous sandstone, and layers of gravel. In these 

 beds there are fragments of wood, legs of crabs, barnacles 

 encrusted with corallines still partially retaining their 

 colour, imperfect fragments of a Pholas distinct from 

 any known species, and of a Yenus, approaching very 

 closelv to, but slio'htlv different in form from, the 

 V. lenticular is, a species living on the coast of Chile. 

 Leaves of trees are numerous between the laminae of 

 the muddy sandstone ; they belong, as I am informed 

 by Dr. J. D. Hooker, 1 to three species of deciduous 

 beech, different from the two species which compose 

 the great proportion of trees in this forest-clad land. 

 From these facts it is difficult to conjecture, whether 

 we here ■ see the basal part of the great Patagonian 

 formation, or some later deposit. 



Summary on the Patagonian Tertiary Formation. 

 — Four out of the seven fossil shells, from. St. Fe in 

 Entre Eios, were found by M. d'Orbigny in the sand- 

 stone of the Rio Negro, and by me at San Josef. Three 

 out of the six from San Josef are identical with those 

 from Port Desire and S. Julian, which two places have 

 together fifteen species, out of which three are common 

 to both. Santa Cruz has seventeen species, out of 

 which five are common to Port Desire and S. Julian. 

 Considering the difference in latitude between these 

 several places, and the small number of species altogether 

 collected, namely thirty-six, I conceive the above, pro- 

 portional number of species in common, is sufficient to 

 show that the lower fossiliferous mass belongs nearV, 

 I do not say absolutely, to the same epoch. What this 

 epoch may be, compared with the European tertiary 

 stages, M. d'Orbigny will not pretend to determine. 

 1 * Botany of the Antarctic Voyage, ' p. 212. 



