62 BRITISH DIATOMACE^E. 



the partial cohesion of their junction-surfaces; valves truncate, 

 marked with moniliform striae ; line of junction distinctly spinous ; 

 junction-surfaces with radiating moniliform striae and three con- 

 spicuous subcentral puncta ; sporangial frustules globular. Breadth 

 of filament -0005" to *0014". Breadth of sporangial frustule 

 •0019". v.v. 



Grev. in Ann. ser. 2. vol. 15. pi. iv. 14-17. Melosira Roseana, Raben, Sussw. 

 Diat. x. Supp. 5 ? 



Fresh water. Forfarshire Mountains, 1847, Dr. Dickie. Cave near Aber- 

 deen, mixed with Orthosira Dickieii, August 1853, Dr. Redfern. Braemar, 

 August 1854, Dr. Balfour. (Cave at Royat, Mout Dore, and Cave under the 

 Grand Cascade, Mont Dore les Bains, June 1 854, TV. Stn.) 



The spinous processes in this species, though very distinct in the dry frus- 

 tule, are apt to fall away or disappear when the valves are immersed in balsam ; 

 owing to this circumstance, Dr. Greville, in the paper quoted above, was at first 

 led to doubt their presence ; but having supplied him with other specimens in 

 a dried state, my acute and accurate friend immediately replied, — " In the 

 material of Orthosira spinosa you have sent me, I see an undoubted fringe of 

 spines." 



Specimens immersed in balsam also appear under the microscope of a much 

 rounder form towards the extremities of the frustules than those in a living or 

 dried state, and might lead the observer to place this species with Melosira ; 

 but the straight uninterrupted margin of the filament, the truncated valves 

 and spinous processes, all conspicuous in the mature condition of the plant, 

 show the propriety of placing it near the last species, and in the genus under 

 which I have ranked it. 



Plate LXI. 386. 



6. Orthosira punctata, n. sp. Filaments direct, or slightly curved ; 

 valves conspicuously cellulate or punctate, with distinct subdistant 

 denticulations along the line of junction. Breadth of filament 

 •0003" to -000/". v.v. 



Fresh water. Ormesby, Norfolk, October and November 1853, Mr. 

 Bridgman. 



A very interesting and beautiful addition to our list of British Diatomacese. 

 Whether Gallionella lineata, marchica, decussata, procera, grantdata, and 

 tenerrima of the ' Microgeologie,' are any or all to be referred to Orthosira 

 punctata, I must leave to be determined by those who possess authentic 

 specimens : the figures in Ehrenberg's great work would lead me to conclude 

 that all these forms are but varieties of the present species. 



Plate LIU. 339. 



