70 



Plaxiphora matthewsi, Iredale. 

 (Proc. Mai. Soc. Lon., vol. ix., June, 1910, pp. 96-100.) 



Frembleya matthewsi, Iredale (Dis. List. Austr. Polypla- 

 cophora, Ashby : Proc. Roy. Soe. S. Austr., vol. xlii., 1918, p. 85). 



I notice this season that each of the three small specimens 

 of the above shell that have fallen to my lot during this 

 summer's collecting have a remarkable feature present on 

 the girdles, previously unnoticed. On reference to my cabinet I 

 find that this feature is present in all my specimens, which 

 include the following localities : Marino, Cape Jervis, Encoun- 

 ter Bay, and Port Lincoln. 



New feature. — The feature referred to is the presence of 

 a large number of slender processes, which for want of a 

 better term we will call spicules, surmounted with strange 

 porcelainous heads. These are not cylindrical, as in Loricella 

 angasi, and which were described in my earlier paper of this 

 year, but are flat on one side and rounded on the other, and 

 are curved like the blade of an oar or scull, but sharply 

 pointed. The surface is highly polished and white, in some 

 lights, showing a few transverse lines ; the stalk, bristle, or 

 spicule, as it is previously called, is in fully-developed speci- 

 mens long and slender and much curved (sickle shaped) when 

 dry. The size of these heads varies considerably; some are 

 fully half the length of the stalk that supports them, others 

 again are supported on long stalks and have shorter heads ; 

 all the heads are broad-based, curved, and pointed at apex. 

 They take their rise chiefly near the outer edge of the girdle, 

 but many are sessile, only the porcelainous blade can be seen 

 pushing out of the girdle amongst the short ordinary spicules 

 which form the girdle fringe. 



Girdle spicules. — The species under discussion has three 

 forms of spicules — if these oar-headed processes can be termed 

 spicules at all. There are the long, coarse, dark brown spicules 

 or bristles that take their rise in bunches at each suture ; these 

 are taper-pointed, like a needle. Then there are a great many 

 short, transparent, rather blunt-pointed spicules that form 

 the fringe of the girdle. Lastly, there are these organs that 

 I have termed oar-headed spicules, the stalks of which are 

 semi-transparent and pale brown. 



Comparisons. — While all the specimens I have collected 

 exhibit oar-headed spicules, I have two, given me by Mr. W. L. 

 May, of Tasmania, from Port Arthur in that State, that 

 show no such spicules, which of course may be due to careless 

 handling, but although Messrs. May and Iredale refer this 

 Port Arthur form to the species under review, there are 

 certainly differences both in the girdle and in the sculpture, 



