NOTES AND CORRECTIONS. 119 
suffered from vertical compression and consequent distortion, so that in many instances it has only been 
possible, even with the choice of numerous specimens, to select one or two as representatives of their 
respective species, and some tablets covered with shells have with reluctance been rejected when specific 
forms could only have been made up by the aid of doubtful restorations. Our note on the age of the 
gray limestone of the Yorkshire coast alludes to the general identity of species which obtains between the 
Testacea of the Great Oolite and Forest Marble /imestones of Gloucestershire and of Oxfordshire; they 
form, in fact, but one fauna, the most prominent species of which are abundant only over very limited 
areas. In the Forest Marble clays we find that the great mass of the organic forms belong to but few 
genera; the deficiencies in this respect are very striking. The large collection of Mr. Walton contains not a 
single Ammonite or Belemnite ; of Gasteropoda there is almost an entire absence of Nerinza, Cylindrites, 
Ceritella, and Trocholoma, genera so abundant and varied in the limestones; these deficiencies are to a 
great extent compensated for by an abundance of special forms of Phasianella and of Acteonina, which is 
the more remarkable as the latter genus is everywhere one of the most rare forms of the limestones. The 
genus Cerithium is abundant, consisting of forms less dwarfed than is usually seen in the limestones. The 
genera Nerita, Trochus, and Monodonta, are well represented, but the two latter genera for the most part 
by forms special to the clays. Of the Conchifera the clays produce Tancredia comparatively in small 
numbers and apparently of few species, but their condition is usually such as will not admit of a rigid 
scrutiny; a similar paucity applies to the Arcas, Trigonias, Limas, and Pectens. Perna, Gervillia, 
Pteroperna, and Astarte, are for the most part represented by species special to the clays or rare in the 
limestones ; Pholadomya, Homomya, Myacites, and Goniomya, appear to constitute the rarest generic forms 
in the deposit ; Cercomya and Thracia, perhaps, are absent altogether. Wanting these, the clay banks 
swarmed with a profusion of Nucule and Cyprine, usually of forms differing from those of the limestones. 
Perhaps about 25 per cent. would be a fair estimate of the testaceous species special to the clays; 
but taking only the more common forms of each deposit, the differences between them are much more 
marked and important than would be inferred from such a proportion of species, 
The following, probably, have not been obtained in any other deposit than the Forest Marble : 
Alaria parvula, p. 22. 
Turbo Burtonensis. Pleurotomaria Bathonica. 
subtexata. Ostrea Wiltonensis. 
nodifera. Gervillia Waltoni. 
Trochus Burtonensis. Perna obliqua. 
Monodonta comma. Trigonia arata. 
Waltoni. Lucina Burtonensis. 
arata. Corbis rotunda. 
tegulata. Corbula Hulliana. 
Onusbus Burtonensis. 
Natica arata. 
texata. 
alta, 
Acteonina Luidii. 
Suessea. 
fasciata. 
Wiltonensis. 
Phasianella variata. 
Solarium turbiniformis. 
Waltoni. 
Islipensis. 
Agatha. 
Corbicella subangulata. 
Cyprina bella. 
Davidsoni. 
Astarte robusta. 
rustica. 
fimbriata. 
ignota. 
Hilpertonensis. 
Tab. III, fig. 12; and 4. cirrus, p. 22. Tab. ILI, fig. 13. 
Further observations lead to the conclusion that the former shell is the young condition of thie latter, 
