Miscellaneous. 451 



intelligible figures than we have had of the early development of 

 any one species of marine Eryozoa thus far. He has, however, not 

 been able to decide positively the nature of the ova, said in oae case 

 to owe their origin to a sexual process, and in the other cases to 

 point to the existence of parthenogenesis among Bryozoa under 

 certain circumstauoes. Claparede has not confirmed the observa- 

 tions of Schneider on the development of Memhranipora ; but from 

 what Nitzsche has observed of the early stages of Bugulu, he appears 

 to have seen the same retrograde development in the youngest stages 

 of its larva which Schneider observed in Cyplionantes during its de- 

 velopment into Memhranipora. — S'dlimans American Journal, May 

 1871. 



On the Order of Development of the Dentition of Sloths (Bradypus). 

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



The skull of the two-toed Sloth {Cholcepus) is distinguished from 

 that of the three-toed Sloths {Bradypus and Arct02)itJiecus\ by having 

 the intermaxillary bone moderately developed, forming the front 

 edge to the jaw ; whereas in the latter two genera it is rudimentary, 

 free, and very commonly lost in preparing the specimen. Bat the 

 development of the teeth, which I believe has not hitherto been 

 observed, differs more. In Cholcepus the front grinders in both 

 jaws are much larger than the others, sub triangular, with bevelled 

 edges, by their rubbing against each other, like the canines of pigs ; 

 they are developed at the same time as the other grinders, or, in- 

 deed, rather before ; for they are of considerable size when the other 

 grinders are small and rudimentary. The front ones of the upper 

 jaw are separated from the others by a considerable space ; and 

 the lower one is considerably behind the produced front edge of the 

 lower jaw, and separated from the other grinders by a moderate 

 space. In the three-toed Sloths, on the contrary, the grinders are 

 all regulaiiy phiced, the front lower one being transversely com- 

 pressed and truncated. The front upper grinder is always smaller 

 than the rest, cylindrical, and it is developed much later than the 

 others. There is a specimen in the British Museum of a young 

 skull of Arctopithecus, which has all the grinders in the upper and 

 lower jaws well developed, but the upper front grinders are small, 

 rudimentary, cylindrical, conical at the tip ; and, on comparing 

 other young skulls, it is evident that these teeth are gradually de- 

 veloped as the animal increases in age, and never attain the same 

 size as the others. 



Note on Asaphus platycephalus. By J. D. Dana. 



The closing remark in my paper on page 368 will have to be 

 cancelled if the species there referred to Asaphus platycephalus is 

 identical with the Asaphus p)latyc.ephcdus {yi. (Isotelus) gigas) of 

 Trenton, the latter (as Mr, BiUings writes the author) often occur- 

 ring, in New York, roUed into a ball. — Silliman's Amencan Journal, 

 May 1871. 



