ZOOLOGY. 735 



sence of postorbital processes." Contrary to what prevails among many 

 other types, " none of the species of this fauna are of larger size thau 

 their modern representatives. In the cases of the beavers, squirrels, 

 and rabbits, the ancient representatives are the smaller." This general- 

 ization, however, can only be regarded as true for Miocene and earlier 

 Tertiary species. Certainly two of the rodent types (without living 

 species) at least were larger than any of their modern relations. These 

 were described by Professor Cope among "the Pliocene and Post-plio- 

 cene rodentia," under the names Castoroides Ohioensis and Amblyrhiza ; 

 the former was the type of an extinct family, the Castoroididre, and the 

 latter related to the chinchillids. The Cantoroides attained to about 

 the size of a black bear, and one of the Amblyrhiza? — the A. latidens — 

 must have been larger than the male Virginia deer. (Am. Nat., Janu- 

 ary, February, April, 1883, vol. xvn.) 



A third kind of Gorpuscule in Blood. — Besides the red and white blood 

 corpuscules, there are indications of a third kind in the blood of mam- 

 mals, but the exact nature of the element has remained obscure. In 

 1883, Bizzozero solved the difficulties of examination, and practically 

 made known for the first time the third kind of corpuscules. They are 

 colorless lens-shaped disks of comparatively small size, having a diam- 

 eter only a quarter to a half that of the red corpuscules and destitute of 

 haemoglobin. • They are especially interesting on account of their sup- 

 posed physiological relations. It is claimed that they are the chief 

 factors in the coagulation of the blood, and that the fibrin is derived 

 from their disintegration. This view is entirely different from those 

 previously enunciated, which referred the fibrin chiefly to the breaking 

 down of the white corpuscules. Investigation of the blood of birds and 

 amphibians revealed an homologous element with the newly differen- 

 tiated corpuscule — pale, nucleated blood-plates, whose functions were 

 similar to those of the mammals. (Am. Nat., vol. xvn, pp. 1303-1305.) 



In a reclamation made to the French Academy of Sciences (Gompte 

 Bendus, vol. 96, pp. 1801-1806) G. Hayem insists that the elements of 

 the blood, to which he gave the name of hematoblasts, are identical 

 with the "plaquettes," or corpuscules, described by Bizzozero. He 

 further contends that Norris's third corpuscular element is a red corp- 

 uscule decolorized as the result of the manipulation to the blood was 

 subjected. [J. B. M. S. (2), vol. in, p. 631.] 



The function of the cochlea of the mammalian Ear. — Years ago Professor 

 Helmholtz, recalling that the membrana basilaris of the cochlea, in which 

 the terminal filaments of the auditory nerve are distributed, increases in 

 width from the bottom towards the upper part, broached a hypothesis 

 to explain the differentiating perception of certain higher tones; it was 

 suggested that " the sound waves that penetrate into the cochlea occasion 

 asynchronous vibration, either in the broader upper half or in the narrow- 

 er lower half of the membrana basilaris, so that the higher tones would 



