IGO 



On Syringammina. 



[Apr. 19, 



the specimens ; nevertheless the radiate tnbular structure and the 

 concentric arrangement of the parts are features common to both 

 forms. On the other hand, the cancellated layers of Parker ia, which 

 form continuous septa of greater or less thickness, are only repre- 

 sented in Syringammina by an open network of anastomosing tubes. 

 Mr. Murray has called my attention to the close similarity that 

 exists between the texture of the natural surface of the recent form, 

 and that presented by some infiltrated specimens of Parkeria, after 

 being etched by means of acid. 



Morphologically, however, Syringammina appears to find a closer 

 parallel in the group of fossil Rhizopods described by Professor Duncan 

 under the term Syringosphwridce * Of these the test in its typical 

 condition is a spheroidal body from 1 to 3 inches in diameter, com- 

 posed of radiating tubes open at their peripheral ends. The tubes, 

 which are branched and inosculating, are arranged in conical bundles 

 radiating from the centre of the test, and the intervening spaces are 

 filled with an accessory network of branching tubes which present a 

 variety of characters. The walls are formed of granular carbonate of 

 lime. The tubes of this fossil type are of much smaller diameter 

 than those of Syringammina, and their association in conical bundles is 

 a very distinctive feature ; besides which, the test presents no evidence 

 of concentric structure. 



The material at present available for investigation is insufficient 

 for any detailed comparison of the structure of these organisms, but 

 it is amply sufficient to show that there exist analogies of great 

 interest between the groups they respectively typify ; and it encourages 

 the hope that living specimens may yet be found that shall satis- 

 factorily elucidate the still doubtful points in the organization of the 

 fossil types. 



EXPLANATION OF THE PLATES. 



Plate 2. 



Eigs. 1, 2, 3. Syringammina fragilissima, natural size. 



1. Inferior aspect, representing an uneven fractured surface near the 



middle of the specimen. The dotted line indicates approximately 

 the original outline. 



2. Superior aspect of the specimen, representing chiefly an uneven frac- 



tured surface near the periphery. At b the exterior is coated with 

 a film of dried sarcode. 



3. Lateral aspect. The portion marked a represents the uninjured 



natural surface. 



* "Karakoram Stones or Syringosphseridse," by Professor P. Martin Duncan, 

 M.B., F.R.S., &c, in the "Beport on the Scientific Results of the Second Yarkand 

 Mission," 4to, 3 plates. Calcutta, 1879. 



Also " On the G-enus Stoliczlcaria, Duncan, and its Distinctness from ParJceria, 

 Carpenter," " Quart. Journ. Greol. Soc," 1882, vol. xxxviii, p. 69, PI. 2. 



