Polythalamian from Transylvania. 355 



shell placed upon its edge is examined in front. In this posi- 

 tion of the shell it is at once seen that the two smaller round 

 apertures are situated close to the middle line of the septum 

 in the neighbourhood of the outer half, while larger oval 

 apertures are placed beneath the small ones. As in sec- 

 tional views the corresponding apertures cover each other, 

 when the shell is looked at from the side only two apertures, 

 one smaller and one larger, are ever to be seen. 



The edges of both kinds of apertures are prominent and 

 drawn out tubularly, an important character which of course 

 appears most distinctly when examined from the side ; in this 

 position of the shell we see upon each septum a more promi- 

 nent tube, narrowing from the base, and a shorter one, the 

 longer of which originates from the larger and the shorter 

 from the smaller aperture, the anterior free extremity of each 

 being marked by an annular thickening. In this respect 

 Entzia tetrastomella approaches the Lagenid'B, the septal 

 oritices of which, according to Biitschli, are produced into 

 tubes *, but it difters from these in the form and number of the 

 apertures. 



I now pass to the finer structure and chemical composition 

 of the shell, and may remark here that in this re-'pect Entzia 

 appears to be one of the most interesting Polythalamia. 



The colour of the shell varies from lighter or darker yel- 

 lowish to deep brown, but generally shows those brownish 

 tints which so frequently occur in chitlnous structures. The 

 substance of the shell conlains angular plates of various sizes 

 and forms, placed close together and entirely imbedded in the 

 foundation-sul'Slance, so that, notwithstanding their presence, 

 the shell retains a smooth surface. On this account I 

 regftvd it as probable that the angular plates are not foreign 

 bodies deposited from without in the substance of the shell, 

 but that they are secreted from the protoplasm and deposited 

 in the shell-substance, and that therefore they never project 

 beyond the surface of the shell. Consequently I adhere to 

 the opinion of Max Schultze, Schneider, and Entz, according 

 to which the siliceous plates of tlie Dijflagics and Pleurophryes^ 

 as well as of Folyinorphina silicea^ M. Sch., are secreted 

 from the protoplasm and incorporated with the substance of 

 the shell. 



The circumstance that the shell is not very brittle, but 

 possesses a considerable amount of flexibility, as proved by 

 variously bent and compressed empty shells, and, further, the 

 great resemblance of the shell in composition, as also in 



* Bioim's ' Kkssen und Ordnungen des Thierreichs,' 2te Aufl. Bd. i. 

 p. rJ7. 



