248 PBOCEEDIIfGS OF THE GEOLOGICAL SOCIETY. [Jan. 22, 



the various species of this group, founded by Young and Bird, Phillips 

 and Eomer, generally on the smallest fragments, might ^th no loss, 

 but much positive advantage, to palaeontology be suppressed. 



M. Astier, who by long residence in the south-east of Trance (in 

 the Neocomian beds of which district the forms we are considering 

 attain their maximum of abundance and perfection of preservation) 

 has had peculiar opportunities for studying the whole group, shows 

 that in the great majority of instances, if not in every one, the 

 species hitherto referred to the genus Crioceras really belong to 

 Ancyloceras. The few Speeton specimens of this group approaching 

 anything like a state of perfect preservation which I have been able 

 to examine are certainly all referable to Ancyloceras, and I have as 

 yet seen no specimen clearly belonging to Hamites or Hamulina. 



With much diffidence, I would venture to indicate the following 

 as among the species of Ancyloceras in the Xeocomian of Speeton. 

 In the Cement-bed occurs a form (Hamites maximus and H. plicati- 

 lis) which seems to belong to the same species as specimens grouped 

 together by Professor Porbes under the name of Scaphites grandis. 

 In the Middle Keocomian we appear to have undoubtedly the forms 

 originally described by Leveille as Crioceras Duvalii and C. Eme- 

 ricii, while lower in the series occur two other forms, C. Puzosianum, 

 D'Orb., and a species near this, but probably distinct (Hamites ra- 

 ricostatus and H. ohliquecostatus). 



Ostreidce. — Ostrea Leymeriei, Desh., has, so far as I yet know, been 

 found only in the highest beds. 



0. frons, Park., occurs in the Upper and Middle Neocomian at 

 Speeton. 



Exogyra sinuata. Sow., of the typical forms (E. latissima, Lam., 

 and E. eloyigata, Leym.) occurs in tolerable abundance in the Upper 

 and Middle Neocomian beds. 



The zone of Ammonites Astierianus is exceedingly well marked by 

 the abundance of the variety (subspecies of Leymerie) E. Coidoni, or 

 E. suhsinuata ; and all of the numerous varieties of this form de- 

 scribed and figured by Leymerie and D'Orbigny may easily be col- 

 lected at Speeton. The little form E. parvula of the former author, 

 which also occui's at Speeton, is probably only the young of one of 

 the others. A very well marked form, however, is the E. suhplicata 

 of Romer, which is confined at Speeton, so far as I am aware, to the 

 Speetonensis-beds. 



It is interesting to notice that many of these species and varieties 

 were noticed in the Speeton Clay by Young and Bu'd. The typical 

 form of E. sinuata appears in the ' Survey of the Yorkshire Coast ' 

 as Ostrea carpax, 0. frons as 0. sinensis ?, and two of the forms of 

 E. Couloni as 0. unguis and 0. quadrata. 



Perna Mulletii, Desh. — This very iateresting and highly charac- 

 teristic species occurs in considerable abundance in the ^' Cement- 

 beds," but has not, I believe, been found below that horizon. 



Lima. — Several remarkably fine species of this genus, some of 

 which are new, occur in the *' Cement-beds " at Speeton. A beau- 

 tiful new species oiAvicula occurs likewise in these beds. 



