COASTS VISITED BY THE ARCTIC EXPEDITION - . 587 



do not appear to be any interstitial tubes, showing that development 

 took place through lateral fission. Indistinctly the corallites appear 

 to have two walls, as in Ac&rvularia, although the crystalline con- 

 dition of the cellular tissue quite prevents this being determined. 

 A large and loosely twisted columella occurs in the centre, arising 

 from the meeting of the septa, of which there are twenty. Tabulae 

 numerous and closely set, giving a highly reticulate character to the 

 corallites. 



Log. Cape Hilgard, lat. 79° 41'. 



Sarcinula, var. of organ um. 



A single specimen only of this variety occurs ; it resembles Litho- 

 strotion irregulare or Martini in its somewhat irregular growth ; but 

 the corallites are even less straight than in those species, and are 

 more reticulate in structure. 



Log. Cape Hilgard, lat. 79° 41'. 



Genus Strephodes. 



Strephodes Austini, Salter. 



Strephodes Austini, Salter, Sutherland's Journ. vol. ii. p. ccxxx, 

 t. 6. f. 6. 



I refer this single specimen also to the above species. M'Coy was 

 inclined to refer Dr. Sutherland's specimens to Olisiophyllum. 

 Owing to the twisted condition of the columellar lamellae, our spe- 

 cimen very feebly shows the twisting of the septa in the centre of 

 the calices ; they certainly were never so columnar or tent-like as 

 in typical specimens of Clisiophyllum. I, however, can only refer 

 Mr. Hart's specimen to the above species, with which it agrees in 

 every particular. It was collected by Mr. Hart from the Upper 

 Silurian beds at Cape Hilgard, lat. 79° 41'. 



Genus Zaphrentis, E-afinesque, 1820. 



Zaphrentis, sp. 



This genus is unknown in Britain from the Silurian rocks. M'Coy 

 records Caninia from the Wenlock Limestone near Wenlock ; but 

 the genus as restricted is chiefly confined, in Britain, to the Carbo- 

 niferous Limestone. In North America, however, six or eight spe- 

 cies occur in the Upper Silurian series. 



The four specimens we have seem to me to be Zaphrentis, but 

 their condition is so crystalline that hardly any septa can be detected ; 

 the costa are coarse and well preserved, the costal lines answering 

 to the number of septa. 



Polished sections afford no real aid, owing to the complete oblite- 

 ration of the interior of the calices ; but there can be no doubt as to 

 the genus being well represented in the Polar seas. We now have 

 it from the Upper Silurian of Offley Island, Bessels Bay, and Dobbin 

 Bay, lat. 79° 41'. 



