124 Mr. H. Seeley on Cambridge Palaontology. 



lines of growth, — thougli it probably thickened with age ; for 

 casts of large specimens show no indications of tubercles. 



The general resemblances come near to T. Fittoni (Dcsh.) ; 

 but the crenulated ridges of that species are not to be confounded 

 with the tubercles of this. The tubercles remind one of T. rudis 

 (Park) ; but their arrangement, and the shape of the cast, which 

 is a third longer than wide, and has the base but shghtly curved, 

 render identification easy. On the casts are thin filais of pyrites. 



Length 2y^g inches; width ly^^ inch; through the valves |f 

 inch. 



lied limestone, near Hunst'on*. 



Coll. Dr. Cookson. Four specimens were obtained. 



The following species have not previously been noticed in the 

 Upper Greensand of England : — 



Ostrea semiplana {Mant.). Nucula albeusis (D'Orb.). 



macroptera {Sow.). simplex (Desk.). 



Exogyra laciniata (Nilss.). ovata {Mant.). 



Plicatula pectinoides {Sow.). bivirgata (J. Sow.). 



Perna subspathulata {Reuss). Leda solea {D'Orb.). 



lanceolata {Gehiitz). ?Veuericardia tenuicostata (Sow.). 



• Rauliniana {D^Orh.). ?Scrobicularia phaseoliua {Phil.). 



All from the immediate neighbourhood of Cambridge. 



EXPLANATION OF PLATES V. & VI. 



Pl. V. Fiff. 1. Ostrea cunahula, from specimens in the collection of Dr. 



Guest. The figure of the lower valve is from a dead shell j a 



small oyster has commenced growing on the inner margin. 

 Fig. 2. Ostrea lagena, a fine specimen from Ashwell. Though the valves 



were united and close, several oysters were found attached to the 



interior. 

 Pl. VI. Fijf. 1. Pecten Barretti. This specimen has a hole, apparently 



drilled by some carnivorous Gasteroj)od. It is the only shell so 



l)erforated which we observed. Upper, under, and side views. 

 Fig. 2. Hinnites trilinearis, upper and under views. 

 Fig. 3. lArca sulcata, enlarged and natural size. 

 Fig. 4. Nucula subelliptica. 

 Fig. 5. Nucula rhomhoidea. 

 Fig. 6. Perna oblouga; a full-grown specimen. 

 Fig. 7. Perna semielUptica; a young individual, in the collection of Mr. 



Carter. 

 Fig. 8. Anomia ? transversa ; a rather small specimen, in the collection of 



Mr. Carter. 

 Fig. 9. Trigonia Hunsf onensis ; a young individual. 



* In a paper recently read before the Cambridge Philosophical Society, 

 an attempt was made by the Author to show the relation of the so-called 

 lied Chalk to the Upper Greensand ; and, as a subordinate member of that 

 formation, it was proposed to name it the Huust'on Limestone. 



