Till'. STEM WD c\l \ \. 41 



the pseudo-lip into a broad plate which lies between the limbs of radials 15 and I), 



ami abuts at the summit against the two posterior deltoids, the shape of which is 

 considerably distorted. Although distinctly a radial at its lower end, its upper part 

 has very much the relations of the anal plate of Elceacrinus, if allowance be made 

 for the fact that the radial sinus of the latter is almost entirely bounded by the 

 deltoids, and not by the radial limbs, as is the case in Granatoctinus Nbrwoodi. 



In a third individual of the latter species (PI. II. fig. 36) the D ray is replaced bj 

 a large and wide plate, which bulges out very considerably so as to distort the shape 

 of the calyx a good deal. It starts from the edge of the basal concavity, but has no 

 definite lip ; though in other respects it resembles the intercalated plate of the two 

 individuals just described. For it separates the limbs of radials C and E, and abuts 

 at the summit against the outer ends of the anal deltoid and of its neighbour on the 

 right. It is doubtful whether there is any deltoid at all in the next interradius 

 (A-E), as the anterior limb of radius E seems to extend right up to the peristome 

 and to be pierced by the spiracle. 



Another curious modification of the Pentremite-type is shown in PI. II. fig. 12. 

 The summit, which is rather distorted, has the usual five ambulacra, though there is 

 no groove on the lancet plate of C. But its place is occupied by a strong median 

 ridge, which is faintly marked by the usual cross striation. This ridge is still mure 

 prominent in the B ambulacrum of a tetrar'adiate specimen, and it has a spiracle- 

 like opening at its proximal end (PI. II. fig. 8). 



Irregularities and inequalities of growth may not unfrequently be observed in 

 the hydrospire-sacs. Thus in the ambulacral section of Pentremites sulcatus, which 

 is represented on PI. XVIII. fig. 5, four hydrospire tubes appear on one side and 

 six on the other; and Ilambach 1 has figured similar inequalities in three other 

 species of Pentremites. 



1 Trans. St. Louis Acad. Sci. 1884, vol. iv. no. 3, j). 544. 



