156 



Mr. H. B. Brady. 



[Apr. 19, 



sandy partitions. More recently, in 1880, on the cruise of the " Knight 

 Errant,"* the rare genus Storthosphcera was found in the warm region, 

 and in the cold area specimens of Comuspira which measured more 

 than an inch in diameter, rivalling in size the finest of the tropical 

 Orbitolites, and therefore amongst the largest known Porcellanous 

 Poraminifera. 



The bottom-dredgings obtained on the cruise of the " Triton " in 

 August and September, 1882, have not been fully examined, but the 

 surface-gatherings made by means of the tow-net are remarkable for 

 the abundance of the curious pelagic type Hastigerina. This genus 

 had not previously been found living in the British seas, and the 

 specimens procured were equal in size and beauty to any of those 

 collected in southern latitudes during the " Challenger" voyage. 



Of the Rhizopoda contained in the dredgings, by far the most note- 

 worthy is the arenaceous form which I propose to describe in the 

 present paper. It may be stated at the outset that two specimens were 

 secured, but owing to the excessively fragile nature of the organism, 

 both were in a more or less fragmentary condition, though sufficient 

 remains to indicate their principal structural features. 



The general appearance of one of the specimens, drawn to the 

 natural size, is shown in PL 2, figs. 1, 2, 3 ; the second was too much 

 "broken to be of service except for purposes of dissection. The figured 

 specimen is about an inch and a half (38 millims.) in diameter, and 

 about eight-tenths of an inch (20 millims.) in thickness, but it is 

 probable that the latter dimension may not be much more than half 

 that of the entire organism ; indeed, it is evident that the test when 

 complete was a rounded mass, which if developed with any degree of 

 symmetry, must have been a sphere of about an inch and a half 

 diameter. The structure revealed by the fractured surfaces is that of 

 a congeries of branching and inosculating tubes radiating from a 

 common centre. 



The fragile nature of the investment is due to the fact that the 

 walls are composed of fine sand with scarcely a trace of inorganic 

 cement. In this respect the organism bears a close resemblance to 

 several well-known arenaceous Rhizopods, notably to Astrorhiza 

 arenaria, but the difference in size renders the absence of incorpo- 

 rating cement a much more noticeable feature ; for whilst the test of 

 the latter species, though loosely arenaceous, has sufficient strength 

 and substance to bear handling without injury, that of the present 

 form will scarcely support its own weight when taken out of water, 

 and crumbles into a mass of sand on the gentlest attempts at manipu- 

 lation. It is hardly possible to lift even small fragments by means 

 of forceps, and the specimen would have been in less satisfactory 



* " Proc. Koy. Soc. Edinb.," 1882, vol. xi, pp. 708-717. 



