IN THE MUD OF THE LEVANT. 45 



round the outer margin of the septa, they form 

 one or more straight lines in its centre. The spe- 

 cimens are also represented as transparent objects, 

 viewed by transmitted light, — by which means a 

 section of the shell is obtained. In the young 

 animal, Fig. 32, it will be seen that only one 

 communicating canal connects the different cells, 

 whilst in the older specimens, these gradually 

 increase in number, until in the outer septa 

 we find several.* The drawing. Fig. 32, also 

 shews the curious thickening of the ring round 

 the septum, which gives the projecting form to 

 the siphuncle — the upper lip being incurved — 

 whilst the lower one assumes the aspect of an 

 obtuse tooth. Fig. 31 shews that the incurved 

 appearance is continued through the whole shell, 

 but only in the outermost series of canals. 



Fig. 34 is a beautiful Planorbis-like form, of 

 which I hare not been able to identify the genus. 

 It is curious as exhibiting no trace whatever of 

 concamerations, though the large and beautiful 



* This indicates that Ehrenberg's division of these animals 

 into Monosomatia and Polysomatia is not a natural one, as 

 in the young state the Peneroplis would belong to the one 

 division, and, in its mature form, to the other. 



