DESCRIPTIONS OF THE SPECIES. 277 



lacra. Mouth small. Anus probably pyriform. Column and ornament not pre- 

 served. 



Remarks. P. acutwm is the smallest species of Phcenosohisma but one with which 

 we are acquainted. Irrespective of size it may be distinguished from /'. Vemeuili 

 (PI. XI. figs. 5, C) by the truncated upper edges of 1 1 1* - interradii, and by the smaller 

 number of hydrospire-slits. The outline of the calyx generally, and the form of the 

 anal interradius distinguish it from P. Archiaci (PI. XII. fig. 10 ; PI. XIV. figs. 5-7). 

 One hydrospire-slit is usually visible for the greater part of its length, although it 

 may occasionally be concealed (PI. XIV. fig. 11). We have had the advantage of 

 studying the original specimen, contained in the " Gilbertson Collection," which 

 was used by the late Mr. G. B. Sowerby in his first description, and afterwards 

 figured by Prof. J. Phillips in his ' Illustrations of the Geology of Yorkshire.' 



Locality and Horizon. Bolland, Lancashire: Carboniferous Limestone. 



PlI^EXOSCIIISMA CARYOPHYLLATUM, de Koninck, Sp. 



(PI. XIV. figs. 1-4 ; PL XVII. fig. 16.) 



Pentremites inflatus, de Koninck (non Sowerby), Rech. Anim. Foss. Terr. Carb. Belgiquc, 



IS 12, p. 38. 

 Pentatrematites Orbignyanus, Roemer (non de Kon., sp.), Arcliiv f. Naturgesch. 1851, 



Jabrg. xvii. Bd. i. p. 358, t. 7. f. 16 a-c (excl. syn.). 

 Pentremites caryophyllatus, de Kon. & le Hon, Mem. Acad. Roy. Belgiquc, 185 1, torn, xxviii. 



Mem, 2, p. 197, t. 7. f. 3, a-c. 

 Pentremites caryophyllatus, Dujardin & Hupe, Hist. Nat. Zoopb. Echinod. 1862, p. 93. 

 Pentremites caryophyllatus, Billings, American Journ. Sci. 1869, vol. xlviii. p. 79, f. 11. 

 Phcenoschisma caryophyUatum, E. & C, Ann. & Mag. Nat. Hist. 1SS2, vol. ix. p. 229. 



Sp. Char. Calyx pyriform, much expanded above, and attenuating rapidly towards 

 the base ; summit more or less expanded and depressed ; section almost circular ; 

 periphery almost equatorial but nearer the summit than the base. Basal plates 

 forming a graceful, short, conical cup, about one third the entire height of the calyx. 

 Kadial plates oblong, much arched both transversely and longitudinally, barely twice 

 the length of the basals ; limbs long, strongly constructed, and not projecting above 

 the summit ; bodies concave in the middle line from the lips to the basiradial 

 sutures ; sinuses very wide and open, with moderately high sloping sides ; lips very- 

 prominent and overhanging. Deltoid plates relatively small, their crests horizontal, 

 or very slightly inclined outwards, but the anal deltoid deeply excavated along 

 almost its whole length. Ambulacra broadly petaloid with the greatest width at the 

 level of the radio-deltoid sutures ; lancet-plates completely exposed ; side plates 

 oblong, scarcely bent down at all. Hydrospire-slits from five to seven, one always 

 remaining uncovered, together with the distal ends of four or even five others. 

 Spiracles present as small obliquely elongated apertures. Mouth small. Anus 

 oblong. Ornament of fine thread-like lines parallel to the margins of the plates. 



Remarks. This species was originally considered by Prof, de Koninck as identical 



