Prof. Bailey on Fossil and Recent Infusoria. 327 



9. Stephanopyxis, nov. suhgen. — This group includes those 

 Pyxidiculae which have turgid bivalve forms with a cellular sur- 

 face, bearing in the middle of the valves a crown of small teeth, 

 prickles, or a membrane. Pyxidicula aculeata is an example. 



10. Xanthiopyxis, nov. subgen. — These forms are Pyxidiculas 

 with bristles, setas, or wings. They have the habit of Xanthidium 

 and Chsetotyphla, but are bivalved and siliceous. Xanthiopyxis 

 oblonga is shown in fig. 14; a similar form occurs at Piscata- 

 way, Md. 



11. " Hercotheca, nov. gen. — Animal e Bacillariis Naviculaceis lib- 

 erum. Lorica simplex incequaliter bivalvis silicea turgida, valvularum 

 membrana continua nee cellulosa, sub cute, utplurimum nervosa, aut 

 sub setis liberis cutis locum tenentibus permanentibusque dividua. Hinc 

 corpuscula in volvularum singularum conliguo summo margine setis aut 

 membranis oppositis coronata et involuta tanquam obvallata apparent. 



" Hse formse Gallionellarum more silicea sed non decidua sub cute 

 sponte dividuntur." 



One species only is described by Ehrenberg. The characters 

 are these : 



" H. mammillaris, testulse valvulis Isevibus basi media setis oppositis 

 simplicibus fere 20, mamraillas superantibus ipsi margini insertis obval- 

 lata. Diameter, -gy. Bermuda." 



12. " Periptera, nov. gen. — Animal e Bacillariis Naviculaceis libe- 

 rum. Lorica simplex insequaliter bivalvis silicea compressa. Valvu- 

 larum testa simplex continua, nee cellulosa. Una valvula turgida nuda, 

 altera alata aut cornuta, cornibus interdum ramosis extremo margini 

 affixis." 



The forms of this genus are allied to those of the genera Rhi- 

 zosolenia and Dicladia, but Rhizosolenia has one central horn, 

 and Dicladia has two, which are also near the centre. Herco- 

 theca differs by the turgid uncompressed form. To the genus 

 "Periptera are now referred (without change of specific names) 

 the fossil forms from Virginia, which were described as Dicladia 

 Cajpra, and D. Cervus, Ehr. I presume that the forms represent- 

 ed in figs. 15, 16, and 17, which I have found frequently in tlie 

 Bermuda Tripoh, are species of Periptera. 



Besides the above genera, Ehrenberg also describes many novel 

 species from Bermuda belonging to genera previously known ; 

 among the most remarkable of which are the following ; to Eh- 



