THE CYST1DEA 



55 



similar folds lead to the oral aperture (possibly conveying nerves to 

 six brachioles). The minor ridges are the superficial indications of strands 

 of mesostroma, uniting plate to plate across the sutures, and emerging on 

 the inner surface in rows of apparent pores. Heliocrinus, Eichw. (1840 ; 

 syn. Heliocystis, Haeck.), Ordovician, Europe, has for type Echinosphaerites 

 balticus, and therefore includes numerous species of similar structure, 

 usually referred to Caryocystis. It differs from Echinosphaera in the more 

 pronouncedly pentagonal, though minute stem, and in the greater orna- 

 mentation of the cup by axial folds and ridges. Stichocystis, Jaekel (1899), 

 has apparent pores in the ridges. Caryocystis was . founded by von 

 Buch (1844 and 1845) to receive Echinosphaera granatum, Wahlenberg 

 (Spliaeronites testudinarius, Hisinger, non Auctt.\ and another species which 



von Buch and all subsequent authors have 

 incorrectly supposed to be S. testudinarius, 

 Hisinger. Eichwald (1859), aware that C. 

 granatum belonged to his own Heliocrinus, justly 

 took as the type the second species mentioned by 

 von Buch, adding to it C. pumila, an Echino- 

 encrinid. The type of the genus is therefore 

 the species universally and erroneously known as 

 C. testudinarius, which name yields to C. An- 

 yelini, Haeckel (Fig. XVII.). Amorphocystit, 

 Jaekel in Koken (1896), is a simple synonym. 

 Caryocystis differs from Heliocrinus in the elon- 

 gation of the oral and aboral poles, and the 

 elongation of the mouth in the sagittal plane. 

 At each end of the mouth-slit, Angelin's figure 

 (1878; our Fig. XVII.) shows two facets for 

 brachioles (Br) ; it also seems to show two 

 openings (hydropore, M, and gonopore .?, G) 

 between mouth and anus. 



FAMILY 2. COMAROCYSTIDAE. Rhombifera in 

 which thecal plates are numerous and inde- 

 finitely arranged. Radial structure of stereom 

 strongly marked, but no definite pore-rhombs or 

 pectinirhombs. Food-grooves on free exothecal 

 brachioliferous processes. Columnals in a single 

 series. Genera Comarocystis, Billings (1854), 

 Ordovician, Canada. Theca ovate, may be over 

 7 cm. high, composed of about 150 mostly 

 hexagonal plates, with strongly marked radial 

 striation of the stereom, especially towards the 



-Br' 



M 



margins, which are raised above the umbones dinarius, Auctt.). (After An- 



p ii -I.. -r .1 TJ. '1 ~ 8 e ' in -) 



r..st 



Fio. XVII. 



Caryocystis Angelini (C. testu- 

 s, Au 



of the plates. Mouth -slit transverse, with a 

 pair of uniserial brachioliferous arms at either end. Theca flattened 

 in mouth-plane. Anus below arms on right side. Hydropore above level 

 of anus, near the posterior margin of the mouth. Stem longer than 

 theca ; columnals low, circular, with moderately wide lumen. Achradocystis, 

 Volborth (1870), Ordovician, Russia, appears to have an anal pyramid of 



