12 On the Genus Pavkeria, Carp. 



to Parheria. I have only had the opportunity ot studying 

 Lqftusia through the medium of thin sections ; but I am 

 quite satisfied that its resemblances to Parheria are super- 

 ficial, and are not indicative of any real affinity. I do not 

 recognize in the structure of Loftusia any thing distinctively 

 Hydrozoal, whilst it possesses structural features, apart from 

 its spiral mode of growth, that are strongly Foraminiferal. 

 Upon the whole, therefore, the present evidence seems to me 

 to fully warrant Mr. Brady's reference of the genus Loftusia 

 to the arenaceous Foraininifera. 



The curious spheroidal fossils which constitute the genus 

 Mitcheldeania, Wethered, present some striking resemblances 

 to Parkeria. The minute structure of the skeleton of the 

 former is, however, in essential respects different from that of 

 the latter, while the chamberlets which are so characteristic 

 of Parheria are wanting in Mitclieldeania. As I have, how- 

 ever, treated fully of the structure of the genus Mitclieldeania 

 in another communication (Geol. Mag., Jan. 1888), 1 need 

 not enter here into a further consideration of its characters 

 and relationships. 



Lastly, there are unquestionable points of resemblance, as 

 well as marked points of difference, between Parheria and 

 the great Hydrozoal group of the iStromatoporoids. No 

 Stromatoporoid, however, possesses the peculiar tubulated 

 coenosteal tissue of Parheria. The nearest approach to tiiis 

 is seen in the genera Stromatopora^ Goldf., titromatoporella^ 

 Nich., and Parallelopora^ Barg. ; but the skeleton- fibre in 

 these genera is vesicular rather than tubulated, and the 

 general structure of the skeleton is fundamentally different 

 from that of Parheria. The genus Labecliia^ E. & H., which 

 miglit in some points be compared wnth Parheria^ is even 

 more widely removed from it than are the above genera as 

 regards the internal structure of the skeleton. 



EXPLANATION OF PLATE III. 



Fig. 1. Tangential section of Parkeria sphcerica, enlarged about ten times. 



p, one of the radial pillars transversely divided ; t, one of the 



zooidal tubes ; c, one of the chamberlets. 

 Fig. 2, Vertical section of the same, similarly enlarged, p, one of the 



radial pillars ; c, one of the chamberlets ; /, calcareous lamina 



supporting one of the concentric lamellse. 

 Fiy. 3. Tangential section of Parkeria, enlarged about twenty times ; tlie 



letters as before. 

 Fig. 4. Vertical section of the same, similarly enlarged ; letters as before. 

 Fuj. 5. Tangential section through one of the periodically-formed layers 



of coarse cancellated tissue, enlarged about twenty times. 

 Fi<j. *>• Central portion of a vertical median section of a specimen of 



Parkeria growing upon a chambered Cephalopod, enlarged 



about ten times. 



