and its Significance in Systematic Zoology, 91 



and anal aperture besides. But it must be borne in mind that 

 the anus in the Polyzoon does not open at the extremity of the 

 body opposite the mouth, as in the archetypal Mollusc, but, by 

 a sudden bend of the intestine, the anal aperture is brought into 

 the closest possible proximity to the mouth, so that, although 

 separate, they both open at the same spot. And let it not be sup- 

 posed that this detracts aught from their position as Molluscs ; 

 for in the highest Molluscs, viz. the Cephalopods, the same thing 

 takes place in a somewhat less degree. Here, again, is a structure 

 which implies great community of general habit. Lastly, there is 

 another most important community of habit between the Polypes 

 and Polyzoa, viz. that, although the Mollusca as a class are ovi- 

 parous, the Polyzoan Molluscs are, in addition, gemmiparous, like 

 the Polypes ; and this power is evidently the secret of the pro- 

 duction of those compound forms which the Polyzoa present in 

 common with Polypes. Hence we see that, with scarcely anything 

 in common except superficial characters, the habits of Polyzoa 

 and Polypes are nearly identical ; and to this fact I would look for 

 an explanation of their identity of form. 



XV. — Observations on two new species of Chiton from the 

 Upper Silurian ' Wenlock Limestone ' of Dudley. By M. L. 

 De Koninck, Member of the lloyal Academy of Sciences, 

 Belgium, &c* 



[With a Plate.] 



On my last visit to England I had the opportunity of studying 

 a great number of new fossils, forming part of the magnifi- 

 cent collection of Mr. John Gray of Hagley, amongst which I 

 observed two species of Chiton, obtained from the Upper Silurian 

 beds of the neighbourhood. 



Before entering into a detailed description of these species, it 

 would perhaps be useful to give a resume of the palseontological 

 works which treat of species of a similar character to those form- 

 ing the subject of these observations. 



Genus Chiton, Linn. 



Established by Linnaeus in 1758 for a small number of living 

 species, this genus for a long time had no representative amongst 

 fossils. 



It was not until the year 1802 that the first species of fossil 



* Translated by W. H. Baily, F. G. S., Acting Palaeontologist to the 

 Geological Survey of Ireland, from the * Bulletins de l'Academie Royale 

 des Sciences, etc. do Belgique,' 26 me annee, 2 me ser., t. iii. 1857. 



