A treatise on zoology . symmetry suggest comparison with Caryocrinidae. Rhomhifera mira,Barr., is usually considered to be aHtejjhanocrintis. Aethocystis, S. A. Miller(1892), Silurian, Indiana, may be placedhere provisionally. Family 5. Malocystidae. Ehombi-fera in which thecal plates are numerousand indefinitely arranged. Radial foldsof stereom often pronounced, but minorrhomb-like striae not clearly seen. Food-grooves on exothecal processes passingover the theca and bearing (when known) in a singleseries. This Ordovician family show^sthe independent evolution of a struct
A treatise on zoology . symmetry suggest comparison with Caryocrinidae. Rhomhifera mira,Barr., is usually considered to be aHtejjhanocrintis. Aethocystis, S. A. Miller(1892), Silurian, Indiana, may be placedhere provisionally. Family 5. Malocystidae. Ehombi-fera in which thecal plates are numerousand indefinitely arranged. Radial foldsof stereom often pronounced, but minorrhomb-like striae not clearly seen. Food-grooves on exothecal processes passingover the theca and bearing (when known) in a singleseries. This Ordovician family show^sthe independent evolution of a structurecommon in a later family, Glyptocystidae^viz. the extension from the mouth overthe theca of series of alternating plates,supporting a single series of alternating series is not so com-plicated as in Glyptocystidae, and thefood-groove passes, not on the top of it, but along its sides. The main grooves appear in all cases to be reducedto two ; but these may branch and wind round the theca as in the later. Fig. XIX. Amygdalocystis florealis. 1, from side ;2,single plate enlarged; 3, portion of food-groove enlarged. Br, dotted outline ofsome brachioles; Br, facet for attach-ment of same. Original, from specimenbelonging to Dr. G. J. Hinde. 58 THE CYSTIDEA form, Sphaerocystis (p. 63), or maj- remain simple, and stretch in thetransversal plane. Genera—Malocystis, Billings (1858), Chazy Lime-stone, Canada. Theca globular. In the type-species the grooves , Billings (1854), Trenton Limestone, Canada. Theca(Fig. XIX.) flattened in plane of food-grooves, and elongate. Groovesnever branched. Family 6. Glyptocystidae. Rhombifera with stem, theca, andbrachioles. The theca composed of five circlets of alternating plates,typically five in each circlet. In first (aboral) circlet, right posterior(r. post.) plate is always fused with right antero-lateral (r. ant.) , with valvular pyramid, between second and third circlets, in rightposterior inter
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