A treatise on zoology . 4). The species referred to this genus by Angelin (1878) are all Ordovician, and agree in the following characters (Fig. XXXVIII.): A spheroid or ovoid theca, sessile on a broad base, composed of irregu-lar plates, the mesostereom of which is pierced by regularly formed 72 THE CYSTIDEA diplopores ; the anus close to the peristome, and with a valvular pyramid ;small hydropore, perhaps combined with gonopore, between mouth and anus, to the left; five oralsseparated by food - grooveswith primitive bilateralarrangement. The variousspecies may be arrangedin groups, according
A treatise on zoology . 4). The species referred to this genus by Angelin (1878) are all Ordovician, and agree in the following characters (Fig. XXXVIII.): A spheroid or ovoid theca, sessile on a broad base, composed of irregu-lar plates, the mesostereom of which is pierced by regularly formed 72 THE CYSTIDEA diplopores ; the anus close to the peristome, and with a valvular pyramid ;small hydropore, perhaps combined with gonopore, between mouth and anus, to the left; five oralsseparated by food - grooveswith primitive bilateralarrangement. The variousspecies may be arrangedin groups, according tothe number of times thegrooves branch, and thenumber of brachiola givenoff from them. Haeckel(1896) has sought to separ-ate as genera {Pomonites,Pomocystis, Pomosjphaera)those with one, two, three,and four brachiola to each ray; but until Angelins notoriouslyinaccurate figures shall have been corrected by observation insteadof by hypotliesis, these names can rest on no sure ground. Moreover,Lovens figure of the type-. Fio. XXXVIII. Sphaeronis globulus, after Angelin. 1, from side, ; 2, tegmen, enlarged. species, S. pomum, repro-duced in our Fig. XXXIX.,shows that the number ofbranches visible may betwo, three, oi- four in asingle individual. Eu-cystis, Angelin (1878), Or-dovician, Sweden (), sends its groovesfarther down the thecathan S2)haeronis, over oneor two circlets of thecalplates. From the distalend of each ray a brachiolewas given off, while othersof uncertain number andposition arose along theside of the grooves. Prob-al>ly some of the formsdescribed by S. A. Milleras Jf(di>rysfitcs should beplaced here ( Tremato-cystis, Jaekel), althoughtheir orals an; not iiyrinKs^ MillercSc (hirley(1894), presents a stage inthe development of food-grooves that in Home respects is more advanceplates have no regular arrangement (Fig. XLII.).
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