40 



Family PLATYCKINID^. 



PLATYCRINUS CORTINA, D. sp. 



Plate III, Fig. 15, lateral view of calyx, ; Fig. 16, summit view 

 with part of the vault, plates, grooves and pores preserved. 



Species medium or rather below medium size. Calyx goblet- 

 shaped; about as high as wide; broadly truncated below; round 

 and slightly contracted immediately above the base, highly convex 

 and protruberant in the region of the arm-bases, so as to give it 

 a marked pentagonal outline when seen from above. Plates thick. 

 Sutures distinct. Surface papillose or very coarsely granular. 

 Column small, round and attached to the base in a radiately lined 

 hemispherical depression. Columnar canal very small and round. 



Basals form a low, round cup, with a slightly expanded sharp 

 rim at the base. First radials about as long as wide, expanding 

 very little above the basals, longitudinally convex, and becoming 

 very protruberant at the articulating facets for the second radials. 

 Articulating facets for the second radials a little more than half 

 the width of the plates and directed outward and upward at an 

 angle of about seventy degrees. Second radials short, axillary 

 and notched for the ambulacral furrows. 



The vault, so far as preserved in our specimen, is only slightly 

 convex. The first radials, between the arm bases, curve slightly 

 toward the vault. There are three plates between the arm fur- 

 rows, the lateral ones form part of the ambulacral covering and 

 the middle one is an interradial proper. There is a pit or pore 

 at the junction or* each interradial with the two first radials at the 

 dividing suture, and there is also a pit or pore on each side of 

 the ambulacral furrows, at the suture lines of the first radials. 

 Whether or not any or all of these are ovarian apertures we are 

 unable to state. The ambulacral furrows are shown in our speci- 

 men as open gutters and we suppose they were covered with 

 small plates, such as cover arm furrows, which have not been pre- 

 served. From some fragments that occur on our specimen, that 

 are not shown in the illustration, we are led to believe that the 

 vault has a central orifice on the summit, possibly covered with 

 small plates, in the same way we have supposed the ambulacral 

 grooves to have been covered. 



