Dr. J. E. Gray on Spatukmys Lasalje. 73 



to interest the reader, I shall confine myself to referring for 

 their description ^o my memoir. The primary cause of rapid 

 death when Articulata are fixed in ice, seems to be the abso- 

 Inte privation of movement and the consequent absorption of 

 the corporeal heat, without any possible restitution. 



III. Action of heat : maximum temperature, 



I have endeavoured to ascertain by experiment tlie highest 

 temperature which our freshwater insects, Arachnida, and 

 Crustacea can endure — in other words, what is the tempera- 

 ture of the hottest water in which they can live. 



I have thus found that the higliest temperatures endured 

 without serious accidents oscillate between 33°'5 and 46°*2 C. 

 ( = 92° and 115° F.), and consequently between very narrow 

 limits. 



These temperatures correspond with those of a certain num- 

 ber of known thermal springs, in the waters of which we may 

 meet with articulate animals wherever the salts or gases in 

 solution have no injurious action upon them. 



If we compare the results with which the aquatic Articulata 

 have furnished me with those wliicli have been obtained by 

 means of animals belonging to other groups, we find that the 

 higliest temperature that aquatic animals, whether vertebrate, 

 articulate, or molluscous, are able to support probably does 

 not exceed 46° C. (115° F.). 



IX. — Additional Notes on Spatulemys LasaliB. 



By Dr. J. E. Gray, F.R.S. &c. 



[Plate II.] 



Colonel P. Perez de Lasala has brought with him several 

 very interesting specimens from his museum, and has kindly 

 presented to the British Museum a fine adult broad-nosed 

 alligator, and a freshwater tortoise from Rio Parand, Corrientes, 

 which is quite new to our collections, and the largest example 

 of the family that has yet been brought to Europe ; I have 

 named it, from its very depressed form, Spatitlemi/Sj and 

 dedicated the species to the enterprising collector, by calling 

 it Spatidemijs Lasalce (Plate II.). 



This species was characterized in the ' Annals ' for 1872, 

 X. p. 463, to which I wish to add the following particulars 

 and comparisons with allied species, and also a figure of this 

 very interesting animal. 



The genus has many similarities to Hydromedusa ; and I 

 thought at one time that it might be the H. tectifera of Mr. 

 Cope, brought from the Parana or Uruguay river, and described 



