258 Br. F. A. Bather — Notes on Yunnan Cystidea. 



these species except 3. splendens Miller & Gmiey (1894). In that 

 species there are said to be 7 Adorals I, but the drawing shows 10. 

 In the drawing (our fig. 28) the suture that should probably separate 

 the two posterior adorals is not shown. If the figure be taken as 

 roughly correct, then each pair of Adorals I enters into the proximal 

 half of a facet ; that is to say, the plates are larger than usual and 

 so reach the actual facet. A similar arrangement is visible in 

 specimen E. 7673 (fig. 29). In H. splendens the distal half of each 

 facet is borne by an Adoral II alternating with the paired Adorals I. 

 Between the five facet-bearing Adorals II are three interradial 

 Adorals II, namely one posterior, one right postero-lateral, and one 

 left postero-lateral. Thus this circlet, as drawn, has the normal 

 number eight, and its difference from the four-facet plan is simply that 

 the anterior Adoral II, instead of being an interradial, bears a facet. 

 Circlet I, as drawn, owes the difference in the number of its plates 

 (10 instead of 6) to the presence of interradial sutures in all 

 interradii and not only in the posterior interradiusi If those sutures 

 were absent, the number and arrangement of the plates would be 

 precisely as in the normal plan. Since Miller & Gurley say that the 

 peristome is " surrounded with seven plates", it is possible that 

 their drawing is wrong in this respect. 



Miller's figure of H. plenus (1878) looks very different, but from 

 his description it is obvious that the Adorals I enter into the facets 

 in the same way as in H. splendens. The figure of H. pustulosis 

 (1878) is so similar to that of H. plenus that the same interpretation 

 of it seems legitimate. As to the number in each circlet, the 

 evidence of these two species is unsatisfactory. 



The drawing of H. sphceroidalis Miller & Gurley (1895) shows 

 eight Adorals II, arranged as in IT. splendens ; but the drawing (our 

 fig. 27) is so clear that it does not seem possible to suppose that 

 Adorals I entered into the facets ; they probably formed an inner, 

 rather obscure rim. The original of H. wykoffi, is crushed and in 

 parts overgrown or missing ; but it is easily interpreted on the lines 

 of H. sphceroidalis. 



Light is thrown on these specimens by the British Museum 

 specimen E 7641 (fig. 26). This has been crushed along lines of 

 weakness starting from the periproct and wandering towards the 

 right anterior corner ; thus some of the sutures in the adoral circlets 

 are obscured. The specimen has been bored, during life, by some 

 organism (possibly a bivalve mollusc) that has made round holes and 

 caused a thickening of the test with obliteration of sutures. In 

 addition the theca has been overgrown by bryozoans and one small 

 pelmatozoan stem, probably after death, and the adoral region is 

 much worn. One can, however, distinguish five facets, and a circlet 

 of Adorals II arranged as in M. sphceroidalis (fig. 27). Indeed, 

 a comparison of the two figures will show resemblances in such- 

 details as the irregular shape of the right posterior Adoral II, and 

 the precise position of the facets on their respective" plates — the 

 anterior being approximately median, while those of the lateral 

 pairs are shifted towards the adjacent interradials, so that the 

 intervals between the facets are equalized. The importance of our 



