466 THE LIAS AMMONITES. 



seen in the Frocester Hill shells, and we miss the two varieties with obtuse backs and 

 distant radii which constitute the varieties ' costula ' and ' regularis ; perhaps, however, 

 these deficiencies might also disappear upon examining good Swabian collections. The 

 septa are identical both in Swabian and Cotteswold shells, the observer should, however, 

 be careful to examine both sides of the Giindershofen specimens, as in one now before 

 me the septa of the right side exhibit a singular abnormal change from the true design, 

 which, however, is perfect upon the left side, and the general figure of the shell has 

 nothing peculiar ; this variability does not occur in Frocester Hill shells. 



" Quitting the examination of specimens I will now advert to the literature of the 

 species ; the first figure and description is that of the ' Nautilus ' opalinus of Reinecke. 

 Quenstedt, in his several works, has figured forms of the variety ' Moorei ' with the 

 volutions much enveloped as Am. opalinus, and has also given examples of Aalensis and 

 of costula as distinct species. D'Orbigny, in his ' Paleontologie Frangaise,' has figured 

 an aged shell resembling the variety ' Moorei,' but unusually inflated, as Am. candidus, 

 afterwards changed to Am. primordialis upon an erroneous idea that it was the species 

 figured under that name by Schlotheim. Upon another plate he has figured both yotmg 

 and aged examples of the allied species Am. Aalensis, which are very truthful in all the 

 details of their ornamentation; a comparison of the septa figured by him of the two 

 supposed species which are taken from some of the last-formed chambers of aged shells 

 will show that in both the pattern and the design are the same, and that the differences 

 are of the most trifling description, if these, indeed, are not attributable to the artist ; 

 the descriptions of Am. primordialis and Am. Aalensis are also substantially alike, if in both 

 we may use the word costa and striae. The author in question makes no reference to the 

 Am. opalinus, Reineck." 



Locality and 8tratigrapUcal Position. — This Ammonite is entirely limited to the 

 uppermost bed of the Harp .-opalinmn zone. I have collected it only in these localities : 

 Frocester, Haresfield, Gloucestershire; and at Burton Bradstock and Chideock Hills, 

 Dorsetshire. 



