284 DAVENPORT ACADEMY OF NATURAL SCIENCES. 



giving a five rayed aspect to the summit. Plates roughened and tuber- 

 culifortn. 



Proboscis sub-central. 



The ornamentation consists of a series of triangles enclosed one within 

 the other, the outer of which— the enclosing triangle heads in the center 

 of the larger plates, meeting there the apices of as many aeries of trian- 

 gles as there are sides of the plates. This peculiarity was traced out 

 first by the artist, Mr. Churchill, to whom the -Academy is indebted for 

 the figures accompanying this paper. 



Fig. 1 represents the base of a specimen, the pentagon enclosing the 

 base being more sharply defined than in the plate. The column in the 

 specimen is slightly removed from the center of the base, the canal pen- 

 talobate. 



, Fig. 2 shows a portion of the plates on the summit, and the upper 

 plates of the calyx, as seen obliquely from the side. 



Fig. 3, though belonging to the next described species, preserves well 

 the normal relations of height and breadth of this species. 



The original of the specimen figured was presented to the Academy 

 by the writer. 



Stereocrinus triangulatus var. liratus (n. sp.). 



Plate xi, fig 3 



This species does not attain the size of the former. Common to both 

 is the same general arrangement and succession of plates. At the same 

 time in this species there is a marked tendency to roundness in the form 

 of the plates. The upper edge of the first radial is slightly curved in- 

 stead of straight, as in *S\ triangulatus. The system of ornamentation 

 is entirely clianged. There is no longer a series of finely marh^d including 

 and included triangles, but a system of sharp, well-defined, prominent 

 ridges, disposed in single or double series, transversing the entire calyx, 

 gathering into sharp nodes at the centres of the several plates. The 

 strength of the ridges is uniform throughout. 



From the base througli the center of the first radial passes a single 

 ridge into the center of the second radial, thence bifurcating it follows 

 the course of the supraradials and brachials, the centres of which are 

 ornamented with nodes. In addition to tliis single ridge, from the cen- 

 ter of the first radial, pass four double ridges, one couplet extending to 

 the center of each adjoining first radial, the other to the center of the 

 nearest first interradial. Tlie first interradials are also distinguished by 

 these, as well as other double ridges, one of which encloses a pit in the 

 center of the plate, its two sides being produced upwards through the 

 second interradial. The other plates abound in single rather than double 

 ridges. The second radial does not attain more than half the size of the 

 first, while the greater part of its surface is covered by strong ridges, 

 drawn out upon the center into a sharp angle. This characterizes the 

 second radials and interradials to such extent that they constitute a 

 girdle of ten nodes, completely surrounding the calyx, giving it a decided 



