444 Chronicles of Science. [July? 



which he showed that they presented a very low type of structure 

 (resemhling foetal teeth), corresponding to the degradation of their 

 function from prehension or mastication to mere incidental " sexual 

 marks." The structure of the recent teeth also threw some light 

 on the nature and condition of fossil cetacean teeth in the Red 

 Crag, called Balaenodon by Professor Owen. 



Dentition of the Mole. — The teeth of the common mole have also 

 recently received attention from Mr. Spence Bate, who is well 

 known for his writings on teeth as well as for his more numerous 

 observations on Crustacea. The dental formulas in Insectivorous 

 mammals is often a matter of extreme doubtfulness, and is one 

 which can only be properly settled by the study of their develop- 

 ment. Fred. Cuvier, Bell, De Blainville, Owen, and Blasius have 

 each assigned a different dental formula to the mole. Mr. Bate has 

 examined the jaws of young moles from the period when they have 

 no hair on the body, and has satisfactorily shown what is the origin 

 and what the antecedents of the permanent teeth. He considers 

 that his observations confirm the formula given by Owen, viz. : — 



i t c 1 pm 7 m I x 2 = 44. 



Mr. Bate's paper was communicated to the Odontological Society, 

 and is published in abstract with a plate in the ' Annals ' for June. 



Bay Society. — 'Nitzsch's Pterylography' is the title of the 

 last volume issued by the Kay Society, having been translated by 

 Mr. W. S. L-allas from the German. Pterylography is the study 

 of the distribution of feathers, and their arrangement in " feather 

 tracts," or " pterylae," on the bodies of birds. Nitzsch was one of 

 the most single-minded and persevering naturalists of his time — he 

 devoted nearly the whole of his life to accumulating material for the 

 present work, and one or two other matters relating to birds, to which 

 class he entirely gave himself up. He died, however, before he could 

 make up his mind to bring together his results. His friend, 

 H. Burineister, who succeeded him at the University of Halle, made 

 it his first duty to do what he could with Nitzsch's material ; and 

 the German edition of 1840 was the result. The present translation 

 is admirably performed, and the ten original plates of small folio size 

 are well rendered. Before Mtzsch wrote, no one had made a philo- 

 sophical attempt to discriminate the dermal appendages of any of 

 the Yertebrata, beyond the rough division into Scales, Hairs, Bristles, 

 and Feathers. He, however, has shown in a most masterly way, that 

 there are definite regions marked out on the bodies of birds, which 

 carry different sorts of feathers, and that these regions or pterylae 

 (feather-forests) can be compared and identified in different genera 

 and species of birds, and that they furnish a means of classifying 

 birds in a very natural way, limiting groups which are otherwise 

 doubtful, and exhibiting their value and importance in other ways. 



