250 F. R. OC. Reed— Woodwardian Museum Notes. 
In the first stages of development it may assume any one of these 
forms. ’ 
Subsequently the indentation or groove becomes so accentuated 
as to divide the shell nearly into two lobes. 
(3) Concurrently with this modification of the ventral valve, a 
sharp narrow depression is developed in a very similar manner 
on the dorsal valve: and this groove increases in depth and joins 
its fellow on the ventral valve at the anterior margin. 
The shells in which this constriction in each valve is strongly 
developed have consequently a most abnormal shape. 
That the malformation is not due to accidents of preservation 
seems obvious by our possession of specimens showing various and 
progressive degrees of its development. It seems that an interruption 
in the growth of the shell must have taken place along the median 
line of each valve. Whether this was owing to the presence of an 
internal parasite, or of some foreign body accidentally introduced ; 
or to disease in the mantle; or to the external application of pressure 
during the life of the brachiopod, is not clear. 
In the majority of brachiopods we know that the sinus occurs in 
the ventral valve and the fold in the dorsal valve, though this fold 
is occasionally marked by a longitudinal furrow. 
But it is interesting to find in Spirifera Urii (Fleming) from the 
Carboniferous, and in the closely-allied Spirifera Clannyana (King) 
from the Permian, a slight indentation in the front edge, and shallow 
mesial furrows in both the ventral and dorsal valves ; these, however, 
are regularly and symmetrically developed. Still their presence is 
suggestive. 
There are some curious malformations in Streptorhynchus crenistria, 
from the Carboniferous, figured by Davidson in his Supplement to 
the British Carboniferous Brachiopoda, pl. xxxvii. figs. 4,5. These 
likewise seem to be due to interruption in growth, and may be 
somewhat analogous to that which produced the more symmetrical 
grooves in the specimens of Sp. lineata above described. 
A strangely distorted form, named Streptis Grayii, from the 
Wenlock Limestone (figured Dav. Silur. Brach. pl. xiii. figs. 14-22) 
has its right or left half twisted higher than the other, and con- 
sequently both valves are longitudinally divided by a sharply curved 
line. Were it not for the twisting, this form would closely resemble 
our abnormal Sp. lineata externally. 
In a few specimens of a Terebratula from the Fullers’ Harth of 
the neighbourhood of Bath in the Woodwardian Museum, indenta- 
tions occur in both valves of a precisely similar appearance as 
those in the abnormal Spirifere; and they seem to have arisen in 
the same manner. 
The exaggerated forms of some bilobed Terebratule and Wald- 
heimie and of Orthis biloba from the Wenlock Limestone caused 
Baron von Buch to compare them with one another; and in spite of 
the great differences of internal structure, Davidson says that similar 
causes may easily have been at work in each case. 
However, I am inclined to hold that in these specimens of Spirifera 
