390 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



It differs from the other incrusting species in the entire absence of oral mucro. 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (com- 

 mon ) . 



Middle Jacksonian: Eighteen miles west of Wrightsville, Georgia (very rare) ; 

 Rich Hill, 5 miles southeast of Knoxville, Georgia (rare) ; one-half mile south- 

 east of Georgia Kaolin Co. Mine, Twiggs County, Georgia (rare). 



Cotypes.C&i. No. 64086, U.S.N.M. 



HIPPOMENELLA LIGULATA, new species. 

 Plate 51, figs. 6-9. 



Description. The zoarium incrusts bryozoa, Orbitoides, or creeps over algae. 

 The zooecia are short, distinct, oval ; the frontal is very convex, smooth, surrounded 

 by a double row of very small triangular areolae separated by some small inter- 

 areolar costules. The aperture is somewhat elongated, semielliptical; a mucro 

 strap shaped, verj r salient, oblique or erect, hides the aperture more or less; the 

 peristome is ornamented with six large distal spines. The ovicell is globular, 

 salient, imbedded in the distal zooecia, elongated, with two very large lateral areas. 

 The two avicularia are placed below the aperture, they are of the same size and 

 very projecting. 



Measurements. Aperture fAa=0.14 mm. . jZs=0.60-0.70mm. 



(exterior) tZa=0.14mm. ' [Z,3=0.40-0.44mm. 



Variations. Most of the time the zoarium is incrusting, but free zoaria are not 

 rare; the lower face is smooth and. according to circumstances, garnished by the 

 hydrostatic apophyses (fig. 7). When the mucro is erect the aperture is quite 

 visible and without the peristomial thickening the species may be confounded with 

 Hippomcnclla aMfera (fig. 6). When it is oblique it hides the aperture more or 

 less (fig. 8). In fossilization the small areolae are easily filled up and disappear 

 (figs. 6, 8, which are the most habitual aspects) ; but superb specimens with areolae 

 are not rare (fig. 9). Then they are triangular and the frontal is covered by very 

 fine interareolar costules coalescent at the mucro. 



Figure 9 perhaps represents a variety, for the two avicularia are much smaller 

 and adjacent to the aperture. 



Affinities. This species differs from Ilippomendla alifera in the salient mucro 

 which ornaments its aperture and which in perspective completes the large peri- 

 stome. 



It is again in this same mucro that it differs from Hippomenella radicata 

 and in the absence of perforated base. 



It differs from HippomeneHa tuberosa in its smaller micrometric dimensions 

 (Z3=0.70 and not 0.84 mm.) and in its nontuberose frontal. 



Occurrence. Middle Jacksonian : Wilmington, North Carolina (common) ; 

 near Lenuds Ferry, South Carolina (common) ; Eutaw Springs, South Carolina 

 (rare) . 



Cotypes.Cat. Nos. 64088, 64089, U.S.N.M. 



