70 



TRANSACTIONS OF THE WAGNER FREE 



Among the forms which retain the small VolutilitJies or Trochoid nucleus 

 in the Eocene, a tendency to variation is clearly observable. To become less 

 regular in form and larger is the tendency. V. cithara illustrates increase of 

 size without loss of regularity, but the most significant changes are in small 

 nuclei, such as those oi Lyria, which begin to appear swollen and asymmetri- 

 cal. This leads to such nuclei as those of Vobita virescens Lam., and through 

 these to the still larger and more ornate nuclei like those of V. musica and 

 further on V. vespertilio, on the one hand, and on the other to larger, but un- 

 ornamented nuclei, as in Valuta niagnifica and Melo indicus, regularity of form 

 being eventually resumed. 



SOAPHELLOID SERIES. 



I. Caricella type of nucleus (PI. 6, figs. 5, 6 ; PI. 7, figs. 2-5, 7, 8). 



Early Eocene. Caricella Leana'D&W, C. WetherelH Soviexhy, C. doliata Conrad (occurring 



in the order named). Valuta Showalteri Aldrich. 

 MiD-EocENK. C. prisca, prceteniiis and C. pyruloides Conrad; C. podagrina Dall. Paris 



Basin Valuta [Eopsephcsa) nmricina and costaria Lamarck ; V. to?-itlosa, neglecta and 



Edwardsi Deshayes, V. mixta (Chemn.) Nyst. 

 Upper Eocene. Caricella reticulata Aldrich, C. subangulata and C. deinissa Conrad ; 



Lapparia pactilis Conrad, L. Mooreana Gabb, L. dumosa Conrad. 

 Miocene. Scaphella Trenholmii T. & H. and S sinuosa Conrad (probably). S. striata 



Gabb, Scaphella obtusa Emmons, S. soliiaria Conrad, Aurinia mutabilis Conrad, A. 



typus Conrad. Valuta Tarbelliana Grat. fide Conrad. 

 Pliocene. Scaphella Jtoridatia Heilprin (probably). 



Recent. Scaphella ancilla Solander, 5. magellanica Sowerby ; .S". angulata Lamarck (pos- 

 sibly) ; Aurinia dubia Broderip, A. Gauldiana and A. robusta Dall. 

 2. Scaphella type (PI. 7, fig. 9). 

 Pliocene. Scaphella Lamberti Sowerby, 5. aurisleporis Sby. ; S. brasiliana Lamarck 



(probably); S. tuberculataSw^nson. S. Trenholmii Twomty & Holmes? 

 Recent. Scaphella junonia Hwass ; S. brasiliana Lam. (probably). 



3. Cymba type (PI. 7, fig. i). 

 Cretaceous. Eucymba ( Valuta) deperdita Goldfuss, and E. (Melo) pyriformis Forbes. 

 Eocene. Eucymba acalana Dall. 

 Recent. All the species of Cymba, C. alia, etc. 



It may be admitted that between the Caricella type and the Scaphella type 

 of nucleus the difference is but slight, yet I have thought it best to keep it 

 discriminated. It is not safe to say that the apical spur of the Caricella type 

 is normally absent until a shell fresh from the ovicapsule has been examined, 

 as I have been able to do in the cases oi S. junonia and S. brasiliana. In the 

 case of S. Trenholmii a.ndfloridana the spur is on the point of disappearing and 

 in the ne.xt generation or specific descendant, S. junonia, it has disappeared. 



