81 



also varies, sometimes being spherical, at others irregularly elliptical. 

 This species I find frequently broken on one side. The average size, 

 measuring, as in the other species, the diameter from the extremes of 

 the opposite tentacula, is from ^^ to -j-^ of an inch. The most per- 

 fect I have seen is in the possession of Dr. Mantell, by whose son, Mr. 

 Reginald Mantell, it was found in chalk flint. I had previously 

 named this species, having long before discovered many, though less 

 perfect. 



The seventh is Xanthidium ramosum, or branched Xanthidium : 

 it is the most common of all the eleven species. There are several 

 varieties ; the tentacula round the apparent circumference varying in 

 number from fifteen to thirty : the average number is about twenty. 

 The characteristic of this species is the branching ter- 

 mination of the tentacula ; the terminations to each ten- 

 taculum are generally three in number, diverging from 

 the end (as in the figure), not unlike a bird's foot, only 

 longer in proportion and more tapering ; but sometimes 

 they are of a more complex structure, each of the three arms or termi- 

 nations branching out again at their extremities (thus) 

 into further processes, resembling the more compli- 

 cated form of another species, which I shall presently 

 notice as the tenth. 



Their average diameter (measured as before) is 

 from the -^ to ?■§>* of an inch. The individuals of this species are 

 frequently found in contact, in pairs, and sometimes as many as three 

 appear to be attached. I possess one which is very remarkable, and 

 the only one among some hundreds which I have discovered. The 

 body is transparent, and within it are three red globules most clearly 

 apparent, of an irregular oval or oblate form, composed as it would 

 seem of a cluster of minute molecules : whether these are ova or 

 clusters of embryo Xanthidia, I cannot determine ; their appearance 

 would favour the opinion that they are, if this be the mode by which 

 they are propagated ; T have figured this in the accompanying plate, 

 No. 13. 



The eighth species is Xanthidium crassipes, or the thick-legged, 

 the name which has been given to it by those observers who have 

 preceded me : and here I would remark, that whenever I could, I have 

 adhered to the nomenclature adopted in a paper furnished by the Rev. 

 J. B. Reade to Taylor's ' Annals of Natural Histoiy, ' and I believe 

 well known to those who are interested about this remarkable group 

 of fossil Infusoria. The dimensions of X. crassipes are of the average 



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