ON THE STRUCTURE OF iENIGMA ^NIGMATICA. 253 



On the Structure of Enigma senigmatica, 



Chemnitz ; a Contribution to our 



Knowledge of the Anomiacea. 



By 



Oilbert C. Boiiiiic, M.A., D.Sc, F.L.S., 



Fellow of Mertoii College ; Linacre Professor of Comparative Anatomy 



in the University of Oxford. 



With Plates 15—17, and 2 Text-figures. 



In a recent paper in the ' Arbeiten aus dem zoologischen 

 Instituten der Universitat Wien/ Sassi (16) has given a full 

 account of the anatomy of Anomia ephippium^ and has 

 elucidated several hitherto obscure points relating to the 

 kidneys and the reno-pericardial orifices in that species. 

 Before Sassi's paper had come into ray hands I had made 

 some observations on the allied genus u^nigma, a tropical 

 member of the Anomiacea, the principal outcome of which 

 has been to confirm Sassi's results. At the same time I have 

 found certain differences between the genera Anomia and 

 Enigma which are of sufficient importance to make it worth 

 while publishing a short account of the latter genus. 



I am indebted to Mr. R. Shelford, of Emmanuel College, 

 Cambridge, and of the Hope Department of Zoology at 

 Oxford, for the specimens of -Enigma senigmatica, 

 Chemnitz, which form the subject of this memoir. They 

 were found living under conditions described by previous 

 authors, on the roots and branches of Nip a (a palm of the 

 family Phytelephantinse) at Sai'awak, and Mr. Shelford tells 



