XArilLlD^. 
83 
not a TrocJioceras, though its young form might have some resem- 
blance to T. cornii-arittis.'’ {BJahe.') 
Remarhs. This appears without doubt to be the “ Xautilus Hol- 
tianits ” of Blake. The specimens, though crushed, give a good 
idea of the character of the shell, one especially showing the coarser 
sculpture and septation very satisfactorily. 
Horizon. AVenlock Limestone. 
Locality. Dudley, Worcestershire. 
Eepresented in the Collection by two examples. 
Barrandeoceras Sacheri, Barrande, sp. 
1867. Xautilus Sacheri, Barrande, Syst. SU. de la Boheme, vol. ii. pt. i. 
p. 149, pi. xxxix. ff. 1-8. 
Sp. Char. Shell discoid, flattened, with scarcely three volutions, 
their breadth nearly double their thickness ; entirely exposed, with 
rather a large central vacuity. The whorls are only slightly en- 
veloping, a very slight groove on the dorsal side marking their 
contact. The young shells are hook-like in shape, their curvature 
not exceeding half a volution. The transverse section is an ellipse 
with a very slight emargination on the inner (dorsal) side. The 
ventro-dorsal is to the transverse axis as 3:2. The increase in 
breadth of the last whorl is in the ratio of 1 : 3. Tlie body-chamber 
occupies nearly half the last whorl, and its capacity considerably 
exceeds that of the whole of the septal chambers. The aperture 
has a very well-marked sinus on the convex margin. The distance 
between the septa, measured upon the sides of the shell, amounts 
to about 4 of the ventro-dorsal diameter ; their convexity equals 
1 of the same. The sutures form a broad and shallow sinus upon the 
sides of the shell, and are strongly arched forwards upon the peri- 
phery. The siphuncle is situated a very little above the centre ; 
its elements are cylindrical. Tlie surface is ornamented with re- 
gular undulations, which may be regarded as feeble ribs, as they 
slightly mark the cast ; they are most strongly developed in the 
young shell, and become obsolete towards the aperture iu adults. 
They have an oblique direction, and thus cross the sutures nearly 
at a right angle, producing a deep sinus upon the periphery, which 
corresponds with the emargination in the aperture, already de- 
scribed. It should be remarked that the ribs tend to become more 
feeble in approaching the periphery. The whole surface of the 
test is covered with fine and somewhat irregular lines corresponding 
in direction with the ribs. The cast of the body-chamber is covered 
G 2 
