CALYPTOCRINIDyE. 341 



zontally, except their extreme lower ends, which take part in the basal 

 concavity. Costals, first distichals and first interbrachials curving rapidly 

 upwards, so that the sides near the top of the cup are parallel with corre- 

 sponding parts of the opposite side. Surface of plates, as shown from the 

 gutta percha impressions, beautifully ornamented with elongate nodes or 

 ridges passing out from the centres of the plates to their sides, but not con- 

 tinued to adjoining plates. 



Basal concavity narrow, and moderately deep. The radials rapidly 

 tapering to their lower ends and rather small, not larger than the second 

 costals, which are considerably larger than the first. First costals quad- 

 rangular, once and a half as wide as long ; the second hexagonal, being 

 truncated at the upper end. First distichals about a third smaller than the 

 upper costals ; the second quite small and the palmars still smaller. First 

 interbrachial larger than the radials, almost as wide as high, those of the 

 second row together smaller than the firsts the interdistichal sub-rhomboidal, 

 the upper and lower angles truncated. 



Horizon and Locality. — Niagara group -, Eacine, Wise, and Chicago, Ills. 



Remarks. — The basal concavity in the casts is deeper than it appears 

 in the gutta percha impressions, and there are shallow grooves passing out 

 from it in a radial direction, which are not seen upon the impressions, and 

 give to the cavity in that state of preservation a decidedly pentapetalous 

 aspect. In specimens in which the plates are but partly dissolved, the sur- 

 faces generally show concentrating lines around the margins of the plates, 

 which probably represent mere lines of growth. 



Eucalyptocrinus ventricosus W. and Sp. (nov. spec). 

 Plate LXXXIIL Figs. 11 and M. 



Sjn. JEucahjptocrims coelatus, Eoemee, 1860 (not Hall 1843) ; Silur. Pauna West. Teim., 



p. 48, Plate 4, Figs. 3 a-e. 



A small species, in its general form subovate, slightly depressed at the 

 poles, its greatest width a little above the arm bases. Dorsal cup low 

 saucer-shaped, the sides evenly rounded, its height less than half the length 

 of the arm compartments ; the plates flat or nearly so, marked in well pre- 

 served specimens by irregular, delicate lines running to the sides, but not 

 communicating with those of adjacent plates. 



Basal concavity narrow and very deep, obscurely pentangular at the 



