Smithsonian miscellaneous collections . , trigeminate; in each poriferous zone 35 pore-pairs inspecimen mm in diameter, 42 in specimen mm in diameter, 12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 145 56 in specimen 30 mm in diameter; the number of primary tuberclesin each ambulacrum varies from 7 in a specimen mm in diame-ter to 20 in a specimen 33 mm in diameter; one large pit in eachambulacrum near peristome (pi. 1, fig. 4) ; primary tubercles verylarge adorally, but greatly reduced in size and number to ambitus. Inter ambulacra.âPlates low, 22 in interambulacrum of specimen1
Smithsonian miscellaneous collections . , trigeminate; in each poriferous zone 35 pore-pairs inspecimen mm in diameter, 42 in specimen mm in diameter, 12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 145 56 in specimen 30 mm in diameter; the number of primary tuberclesin each ambulacrum varies from 7 in a specimen mm in diame-ter to 20 in a specimen 33 mm in diameter; one large pit in eachambulacrum near peristome (pi. 1, fig. 4) ; primary tubercles verylarge adorally, but greatly reduced in size and number to ambitus. Inter ambulacra.âPlates low, 22 in interambulacrum of mm in diameter, 24 in specimen mm in diameter, 28 inspecimen 30 mm in diameter; primary tubercles very small in areaextending from apical system to slightly above ambitus, no tuberclesin median region, one tubercle on each plate near adradial suture, insome specimens tubercles smaller on every other plate in some series;tubercles very large in area from slightly above ambitus to peristome;usually two tubercles on each Fig. 4.âArbacia crenulata Kier, new species: Apical system of holotype, 648133, from the Buckingham fades of the Tamiami formation,from loc. 20, X 4. Peristome.âVery large, one-half as wide as horizontal diameterof test, pentagonal, relative size of peristome constant throughoutadult growth (text fig. 5) ; gill slits wide, continuing considerabledistance on surface of test (pi. 1, fig. 4) ; auricles high, slender, notjoined. Periproct.âOpening elongated along line passing through inter-ambulacra 1 and 3; size constant throughout growth (text fig. 6). Tuberculation.âAll primary tubercles imperforate, smooth, onhighly inflated bosses; surface of all plates, where tubercles do notoccur, crenulated with series of narrow grooves and ridges runningfrom apical system to peristome (pi. 1, fig. 5). Number of tuberclesrelative to size constant throughout growth (text fig. 7). Comparison with other species.âThis species is very similar to no. 5
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Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
