Geological Society. 243 



Lyme Regis, and was embedded in an ovoid nodule of indurated 

 Lias. 



Owing to the complete envelopment of the skull and its subse- 

 quent pyritization, the bones and delicate interorbital septum are 

 preserved in perfect condition, permitting the accurate delineation 

 of the openings for the nerves. The bones apparently are com- 

 pletely ossitied, and the entire build is massive, the heavy outer 

 cartilage-bones receiving support internally from the well-developed 

 orbitosphenoids. The supraoccipital, which alone exhibits signs of 

 erosion, shows clearly the bony texture. 



There is no foramen in the parasphonoid in front of the basi- 

 pterygoid processes, as in Lepidotvs. 



The basicranial canal differs from that in Amia ccdva, in its 

 extension to the rear of the skull, that in Amia ending in a 

 cul-de-sac half way. 



The third, fourth, and fifth nerves in Dapedius have their most 

 probable entry through a large median opening between the 

 orbitosphenoids, and not as in Amia from the basicranial canal. 



The opisthotics are stout and prominent bones, with an upward 

 inclination corresponding to that of the parasphenoid. 



The foramina for the optic and olfactory nerves are clearly 

 shown, the latter nerve having been exposed for about two-fifths of 

 its course across the orbit, thereby differing from Amia and Lepi- 

 dotus, in both of which it is enclosed in canals. 



There are two openings between each orbit and the nasal fossa. 



The basioccipital exhibits a small condyle on each side, and is 

 produced posteriorly in a process above the entrance for the 

 notochord. 



April 9th, 1913.— Dr. Aubrey Strahan, F.H.S., President, 

 in the Chair. 



The following communications were read : — 



1. ' The Variation of Planorbis multiformis Bronn.' By George 

 Hickling, D.JSc, F.6.S., Lecturer in Palaeontology & Demonstrator 

 in Geology in the Victoria University of Manchester. 



The writer gives an account of an investigation of the above- 

 named Miocene gasteropod, based on a suite of 532 specimens from a 

 single block of stone. The shells of this type from the Steinheim 

 deposits were formerly investigated by Steinmann, Hilgendorf, 

 Hyatt, and others. Many species and subspecies were founded by 

 those writers, who also constructed genetic series which were 

 described as following a stratigraphical sequence. The specimens 

 considered in the present paper include several of the species and 

 subspecies of Hyatt. Since, however, these individuals were clearly 

 all living together, aud all tho types appeared to pass ono into the 

 other by insensible gradations, it seemed doubtful whether they 

 could properly be regarded as constituting more than a single 



