and their relation to existing Animals. 121 



forms which agreed in their structure : a few have been added by 

 him more recently. Of those twenty-one, only ten have been 

 found in Barbados ; and of the additions recently made, only a 

 part are to be found in the rocky masses of Barbados. These 

 results lead to the conclusion, " that the Polycystina of Barbados, 

 as far as they have been examined, resemble only in a few in- 

 stances forms now living, and come nearer in structure to those 

 which are contained in the rocks of the secondary period than in 

 those of the tertiary formation." 



Of other siliceous forms which constitute the rocky masses of 

 Barbados, Professor Ehrenberg mentions, besides the Polycystina, 

 three other groups : — 



1. Some of the specimens of rocks contain shells of Polygastric 

 Infusoria ; in others they are entirely absent. Of eighteen spe- 

 cies with siliceous shields found in Barbados, only one agrees 

 with the chalk formation of Sicily, and only two with those found 

 in the tertiary rocks of Oran, Engia, Zante, Virginia and Ber- 

 muda. It is very remarkable that many of the Barbados forms 

 of animalcules are quite peculiar, and do not occur in any other 

 locality on the globe as far as hitherto known to Professor Ehren- 

 berg. A number of these new and peculiar forms constitute three, 

 or perhaps four new genera, which Professor Ehrenberg calls Acti- 

 nogonium, Dictyolampra, and Liostephania. Biddulphia cirrhus, a 

 new species, is very abundant, and the new genus Liostephania 

 with its varied forms apparently constitutes three new species. 



2. The Phytolitharia consist of fragments of Spongilla and 

 Tethya, of which only a few are peculiar. Professor Ehrenberg 

 described twenty-seven species. The most remarkable form ap- 

 pears to be Spongophy Ilium cribrum, which is likewise found in the 

 rocks of Caltanisetta, but it is much more frequent in the marls 

 of Zante, where it occurs almost in masses. Amphidiscus annu- 

 latus and Spongolithis annulata are especially distinguished in 

 their structure. The Spongophyllia are so remarkable that Ehren- 

 berg considers them the commencement of a new series of forms 

 hitherto unknown, belonging neither to Tethya nor to Spongia. 

 Phytolitharia derived from freshwater or terrestrial plants do not 

 occur in any of the rocks. 



3. The third group of siliceous fragments in the Barbados 

 marl consists of perfectly new and very peculiar forms, which 

 are called Geolithia by Ehrenberg. They are regularly formed 

 and consequently easily recognizable, and considered as sili- 

 ceous fragments of animals, they may prove as useful for geo- 

 logical purposes as Phytolitharia are with respect to plants, and 

 Zoolitharia in calcareous fragments as regards animals. They are 

 neither fragments of Spongia nor of Tethya) but occasionally 

 parts of Polycystina are recognized. Ehrenberg frequently ob- 

 served the beaks and heads of Eucyrtidia, or the nuclei of Ha- 



Ann.^; Mag. N. Hist. Vol.xx. 9 



