78 The FatlioJogical Relations of the 



the valves of the extinct and the recent forms. Their structure 

 and ornament afford excellent subjects for microscopical work, and 

 the geologist prizes the Estheria as being evidence of brackish 

 water having alternated with marine, and as indicating (in the 

 Trias, for instance,) the occurrence of lakes and lagoons where the 

 main mass of fossils and their surroundings seem to speak of marine 

 conditions.* For Leaia,.! know of no closely corresponding recent 

 analogue, and even among fossils the still enigmatical Myocaris f 

 and Bibeiria J are the only probable relations as yet observed. 



Postscript. — At page 185, vol. iv., for Gyprella subannulata 

 read Ci/prella chrysalidea, De Koninck, var. subannulata ; for 

 Entomis divisa, read Entomidella divisa ; for Beyrichia Wilcken- 

 ziana, read Beyrichia Wilchensiana. 



At page 18(3, to the Cypridae add the genera Groniocypris and 

 Metacypris. 



At page 187, to the Cytheridae add Polycheles. 



Delete Cylindroleberis, this being a synonym of Asterope. 



The genus Entomis should be separated from the Cypridinadse, 

 and with Entomidella be arranged as a distinct family (Ento- 

 mididw). 



VI. — The Pathological Relations of the Diphtheritic Membrane 

 and the Croupous Cast. By Jabez Hogg, Surgeon to the 

 Eoyal "Westminster Ophthalmic Hospital, President of the 

 Medical Microscopical Society of London, &c. 

 {Read he/ore the Medical Microscopical Society, June 20, 1873.) 



Considerable misapprehension appears to prevail with regard to 

 the pathological relations of the felt-like membrane usually secreted 

 in diphtheria, and the filmy viscid substance thrown off in croup. 

 You will therefore, I think, agree with me that the subject is one 

 of sufficient importance to bring under discussion in the Medical 

 Microscopical Society ; the question being one of equal interest in 

 a medical and a histological point of view. 



One often hears of practitioners endeavouring to decide between 

 an affection, croup with a mucous-looking membrane, and diphtheria 

 with a true membrane, and in which the constitutional disturbance 

 is quite remarkable ; and then, apparently without having formed 

 an opinion as to their true nature, or arrived at a settled conclusion 



* Jones, ' Quart. Journ. Geol. Soc.,' vol. xix., pj'. H7, 153, &c. 



t Salter, ' Geol. Mag.,' vol. i., p. 11. 



X Sharpe, ' Geol. Soc. Journ.,' vol. ix., p. 158. 



