74 



THE CYSTIDEA 



M 



A s - 



half-way over the tlieca, crossing the sutures of the plates, and giving off 

 short branches on either side, or sometimes on one side only, at irregular 

 intervals. At the ends of the branches are facets (Br) for the support 

 of brachioles. The grooves are shallow and have minute covering-plates. 

 The anus (As), of which the valvular pyramid is rarely preserved, lies about 

 a third of the way down the theca ; between it and the mouth are two 

 openings, a little to the left, viz. a small round gonopore (G) and a madreporite 

 (M). The latter, the representative of the hydropore, is always close to 

 the first brachiole-facet of the left posterior groove, at the junction of three 

 plates ; it consists of folds (slits ?) running at right angles to the sutures, 

 and is bounded by a slight ridge forming a triangle or trapezoid. According 

 to Volborth, there was at the aboral pole a stem, ^ to width of theca, 

 with a wide lumen, and low columnals with five longitudinal sutures, and 

 with encrusting root-expansion. Eichwald, however, could not find more 

 than a short conical extension of the theca, and this agrees better with 

 the appearances of specimens sent by Volborth to the British Museum. 

 Fungocystis, Barrande (1887), Ordovician, Bohemia (Fig. XLIV.), differs 



from Glyptospliaera in the broad base, 

 hollowed for attachment to some marine 

 object, and forming an angle with the long 

 axis of the theca ; the paucity of diplo- 

 pores ; and the regular alternation of the 

 groove branches, making each groove a zig- 

 zag. The test itself is not preserved ; the 

 internal casts show no sign of the external 

 grooves and brachioles ; but they show 

 between anus and mouth a curved eleva- 

 tion (madreporite 1). 



FAMILY 3. PROTOCRINIDAE. Diploporita 

 in which the food-grooves extend over the 

 theca almost to the aboral pole, and are 

 regularly bordered by alternating thecal 

 plates ("adambulacrals"), on which are 

 the brachiole-facets. Diplopores diffuse or 

 confined to adambulacrals, from which they 

 are never absent. These represent a further 



advance in precisely the same direction as previous families. Genera 

 Protocrinus, Eichwald (1840), Ordovician, Russia (Fig. XLV.), was well 

 described by Volborth (1846). Theca spheroidal or ovoid, attached by 

 a stem in the young, but free in old age and losing all traces of attach- 

 ment (cf. Lichenoides). Thecal plates larger, stouter, and more swollen 

 than in Glyptospliaera ; all bear diplopores, which may become somewhat 

 at right angles to main food-groove, on the adambulacrals. The main 

 grooves are rather straighter than in Glyptosphaera, lying regularly between 

 large alternating thecal plates (adambulacrals), each of which bears a 

 brachiole, except one or two of the proximal ones on the side towards the 

 direction of the clock -hands. Hydropore minute, above anus. Proteroblastus, 

 Jaekel (1895; syn. Dactylocystis, 1899), Ordovician, Russia (Fig. XLVI.). 

 Theca ovoid, sometimes prolonged gradually into a stem (cf. Dendrocystis). 



Fungocystis rarissima, recon- 

 structed on the evidence of 

 Barrande's figures ; enlarged. 



