DECAPOD CETJSTACEANS OF THE OXFOED CLAY. 



543 



which I have very courteously been allowed to consult, collec- 

 tively form materials for a more complete knowledge of the Ox- 

 fordian Crustaceans than has hitherto been possible. 



I will first allude to the forms which have been obtained from 

 St. Ives, and afterwards briefly notice those from other localities. 



The consideration of a group of fossil forms found associated in 

 any one particular horizon has always a special interest, both 

 biological, palaeontological, and geological ; and the degree of interest 

 depends in great measure ypon the precision with which such strati- 

 graphical position can be defined. Therefore, before describing the 

 fossils, I will point out the horizon from which they were obtained. 

 I am able to do this definitely by the kindness of Mr. Koberts, 

 E.G.S., of the Woodwardian Museum, who has recently critically 

 examined the district of St. Ives, and has embodied the results of his 

 observations in the yet unpublished essay which has secured to him 

 the honour of the Sedgwick Prize. Mr. Roberts states that — " The 

 fossil Crustacea found at St. Ives come from the large clay-pit which 

 lies immediately to the west of that town. The pit is opened in the 

 Oxford Clay, and, at the present time, shows the followiDg section : — 



Section in Clay-pit west of St. Ives. 



St. Ives Eoek 



Oxford Clay... -! e 

 I 



m. 



St. IvesEock 3 



Oxford Clay, (a) Dark blue clay 8 



{h) Calcareous nodules 9 



(c) Dark blue clay 15 



{d) Calcareous nodules 9 to 10 inches. 



(e) Argillaceous limestone 1 



{/) Blue clay, which at one time 



was worked to a depth of ... 16 



ig) Limestone (thin bed) 



