112 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
This is in part the M embranipora corbula group of Waters. The recent species 
belonging to the genus are as follows : 
Ilincksina ( M embranipora ) ~ftustroid.es Hincks, 1880. 
Ilincksina {JS1 embranipora) pynda Hindis, 1881. 
Ilincksina ( Merab ranip o ra ) maderensis Waters, 1898. 
Ilincksina (M embranipora) sceletos Busk, 1858. 
Ilincksina (M embranipora) minuscula Hindis, 1882. 
Hincksina (M embranipora) defensa Kirkpatrick, 1888. 
Ilincksina (M embranipora) corniculifera Hindis, 1882. 
Ilincksina (M embranipora) inarm ata Hincks, 1881. 
In this genus opposite spines may be able to unite and form a frontal analogous 
to that in the Costulidae, but this is not a general phenomenon, as it occurs only in 
very rare zooecia. 
The species of Ilincksina which we have distinguished may be separated into 
two groups. Those of the first section have small spines and avicularia little dif- 
ferentiated, while those of the second section are more typical. 
Description. — The zoarium incrusts small pebbles and bryozoa. The zooecia 
are elongated, elliptical, distinct ; the mural rim is thin, salient, rounded, almost 
equal throughout, bearing with some irregularity from six to eight lateral and two 
distal spines. The opesium is large, entire, elliptical or irregular. The ovicells 
are very small and are manifested only as small distal convexities. 
Variations. — On all of our specimens the lateral spines are very imperfectly pre- 
served, but the two distal spines are more constant. The mural rim is generally 
thin, but it may become a little broader (fig. 2). The gymnocyst is much reduced 
and generally absent. The primoserial zooecia are often modified avicularian 
zooecia little differentiated. Regenerated zooecia are rare. 
Affinities. — This species differs from Hincksina jacksonica in its incrusting 
zoarium and its more visible spines. 
It differs from Hincksina smithi in its mural rim, which is never enlarged at the 
base, in its larger micrometric dimensions, its smaller ovicell and in its more in- 
constant spines. 
It differs from Hincksina vicksburgica in the absence of all proximal crenula- 
tion of the opesium. 
Among the recent species it has the greatest affinity with M embranipora 
pyrula as figured by Hindis 1 in 1881, but the ovicells are totally different. 
DIVISION I. AVICULARIA LITTLE DIFFERENTIATED. 
HINCKSINA REPTANS, new species. 
Plate 22, figs. 1-3. 
1 Annals and Magazine Natural History, ser. 5, vol. 8, 1881, p. 51. 
