MONOGRAPH OF THE EXISTING ORINOIDS. 537 



'Ilie basals, which are not quite so long as the orals, foim a cup which is 

 relatively high, slightly broader than long, with slightly convex sides. 



A minute radial is present in each of the angles between the basals and the 

 orals, and in one of these angles a much larger plate — the radianal — has developed 

 just to the left of and in the same plane with the radial. 



The orals are peculiar in having the distal angles somewhat produced, broad- 

 ened, and flattened. An area having a surface which is approximately a spherical 

 triangle reaches from the entire proximal border as a base to an apex which lies 

 in the median line halfway between the base and the tip, and follows the contour 

 of the body. From this portion the lateral regions, which form narrow triangles 

 with the apices at the proximal lateral angles, bend outward at a slight angle, 

 distally adjoining the narrowly fan-shaped anterior process, of which the apex 

 touches the apex of the spherical triangle just described, and the rounded side 

 opposite forms the distal border, which is itself slightly bent backward, its plane 

 making a slight angle with the plane upon which the spherical triangle rests. 

 The basals, therefore, show essentially the same characteristics as those of Tlathro- 

 metra proli-xa, but the angle which the lateral portions make with the depressed 

 central portion is not nearly so great, and the tip, instead of being carinate in 

 such a way that when the orals are closed the five keels come into mutual contact 

 for their entire length, is flattened and elongate fan-shaped. 



No. 10 : Dredged on June 16, 1902, in 385 meters. 



A badly broken specimen in the stage just before the appearance of the 

 radial structures. 



No. 11 (fig. 890, p. 533) : Dredged on February 7, 1903, at a depth of 350 meters. 



Total length (distal portion of column missing), 2 mm.; length of crown, 

 0.3 mm. 



There are 10 columnals in the remaining portion of the column. 



Rounded infrabasals appear to be present. 



The basals form a deep cup slightly broader than long. 



A small rounded plate — the radianal — is present in one of the angles between 

 the basals and orals, situated just to the left of the plane dividing them. 



Tn their proximal half the lateral borders of the orals are parallel; in the 

 distal half they converge to the broadly rounded tip; the lateral borders are 

 turned outward, and the distal apex is slightly produced. 



No. 12 (fig. 891, p. 533) : Dredged on February 15, 1903, at a depth of 400 meters 



Total length (distal portion of column missing), 2.2 mm.; length of crown. 

 0.6 mm. 



There are nine columnals remaining, of M'hich the first four are short and dis- 

 coidal and the following rapidly become elongated, so that the ninth is about 

 four times as long as broad. 



Infrabasals appear to be present. 



The basals form a broad well-rounded cup. which is much broader than hiwh. 



The radial.s are .small, but well defined, rhombic p1.ates !3'ing in the ano-les 

 between the basals and the orals. 



