394 G. B. Pritchard: 



A peripetalous fascicle entering the interradia, a lateral 

 fascicle starting from the peripetalous close to the antero-lateral 

 ambulacra and passing beneath the periproct. 



Tubercles crowded, largest actinally, usually crenulate and 

 perforate, and either on flat or in sunken scrobicules. 



T. — Linthia mooraboolensis, sp. nov. 

 (PI. XXTI., Figs. 1, 2; PI. XXITL, Figs. 3, 4). 



Description. — The test is very much depressed, and quite as 

 tumid post-medially on the base or actinal surface, as behind the 

 apex on the abactinal surface, becoming relatively much more 

 flattened towards the anterior margin. The marginal contour is 

 circular to very slightly elliptical, there usually being a little 

 greater length in the antero-posterior diameter ; deeply but 

 narroAvly grooved in front, where the odd anterior ambulacrum 

 runs, and the groove is not of uniform width, having its 

 maximum width about midway between the apical system and 

 the anterior margin, and its minimum width, which is about 

 one-third of the maximum, at one-fourth of this distance from 

 the anterior. The anterior groove indents the margin to the 

 extent of one-tenth of the antero-posterior diameter. 



Upper surface very slightly convex, greatest convexity in the 

 posterior interambulacrum, but not strikingly keeled. 



Seen in lateral profile the maximum height of the test is situ- 

 ated at one-third the diameter from the posterior margin 

 abactinally gradually sloping to the anterior and posterior, 

 actinally almost flat to the peristome, but running up at very 

 low angle to the periproct. 



The transverse profile is biconvex, more regular dorsally, but 

 vent rally flattening towards the ambitus, which in consequence 

 is not very tumid, but rather suddenly rounded. 



Sternum convex, broadly lanceolate, well defined laterally 

 by the posterior ambulacra, with two strong posterior tumidities, 

 between which a shallow groove runs up to the elliptical peri- 

 proct, the latter being obliquely set immediately below the 

 margin. Peristome large, semilunate, eccentric to the front, 

 and very close to the anterior notch, with a strongly swollen 



