40 
GEOLOGY 
lisbed, 1857, under the title: On the Geology of Southern Africa f Trans, of the Geol. Soc. of Ijtndon, 
second series, vol. VII, page 175.), show that the secondary strata of Algoa bay are more pro- 
bably Jurassic than Cretaceous; and Sharpe, who described the fossils collected at Sunday river 
and Zwartkop river by Dr. Atherslone and A. G. Baines, thought the forms of these fossils re- 
sembled very much those found in the middle and lower part of the Oolitic series of Europe. The 
probability is therefore that the Jurassic formation exists in Southern Africa. This Gryphwa imbrkata 
or G. Darwinii does not resemble the G. Couloni, as Krauss thought, but on the contrary is much 
like the G. arcuata of the lower Lias, from which it differs by its oblique beak and its form be- 
ing more elongated and laterally compressed. 
Explanation of figures. — Plate IV, fig. 5. Inside of lower valve. 
» IV, fig. 5 a. Outside of lower valve from another specimen. 
» IV, fig. 5 b. Inside of upper valve. 
» IV, fig. 6. Young individual with both valves. 
HOLASTER COMANCHESi n. sp. 
Plate III , fig. 3,3a, 3 b. 
Description. — Shell oval, cordate, very convex, longer than it is wide, enlarged and sinuous in front, acu- 
minated at the opposite side. The top of the shell is very convex and slightly pointed, the point corresponding 
to the apical disk , and is placed a little in advance of the middle of the total length. Underneath the shell is en- 
tirely flat, excepting a slight elevation towards the rear, and a little depression in front and on the sides of the 
mouth. The anterior sinus from the mouth to the apex is straight, shallow, rounded, and disappears entirely be- 
fore reaching the apical disk. The mouth is large, transversely oblong and placed near the anterior edge. The 
anal extremity is obtusely truncate, with a vertically elliptical orifice, placed at about, or a little lower than, hall 
the height of the test. The ambulacra are straight, regularly radiate and linear lanceolate, extending to the outline 
of the shell, and increasing gradually in width to the inferior margin. The pores are transverse and oblong, lliere 
are rather large tubercles not far from the apex in the interambulacral spaces; these tubercles are very numerous 
on the under side of the shell and are all perforated and set upon bosses with crenulated summits. The apical di.sK 
is very indistinct and c.annot be described. 
Observations. — This species is nearly allied to the Holaster sunplex Shumard (Paleontology of the 
Exploration of the Red river of Louisiana^ in the year 1852, by Capt. R. B. Marcy , p. 210, pi. Ill, fig. 2.), 
and for a long time I thought it identical. The figure of Shumard is so badly lithographed , and fui-ther 
his specimen being broken near the anus, that the drawing is useless; but in his excellent description 
Shumard says that the ambulacra are flexuous, while in the H. Comanchesi they are straight, and the 
H. simplex is a shell regularly rounded superiorly , while this species is a little pointed and consequently 
not regularly rounded. The Holaster Comanchesi has also numerous points of resemblance to Holaster 
(Ananchytes) fimbriatus Morton (Silliman’s Journal, vol. XVIll . p. 245, pi. 3, fig. 9.); Holaster subglo— 
bosus Agass. [Description des Echin. Fos. de la Suisse, p. 13, pi. 2, fig. 7 — 9.); Ananchytes (Holaster) sub- 
globosa Forbes [Brit. Org, Rem., decade IV. pi. VII.), and especially to the Holaster Trecensls I.eymerie 
(in d’Orbigny’s PaUontologie fran^aise, Ter. Cret.; tome VI, p. 101, pi. 817.). 
Locality. — This fine specimen was found in the Cretaceous rocks of the borders of Hed river 
near Preston , Texas. 
Explanation of figures. — Plate III, fig. 3. Shell natural size, seen from above. 
» HI, fig. 3 a. Same, beneath. 
» HI, fig. 3 b. Same, vertical jirofile. 
N. B. — I have collected or met with many other fossils from the Cretaceous rocks of Texas, 
the Prairies and New Mexico. But some have been already described by Morton , Roemer, Owen 
