[MATTHEW ] ACROTHYRA AND HYOLITHES 95 
Lingulella. From this it seems natural to infer that the genus had a 
long pedicle as in Lingula and Lingulella. 
F. Blochmann who has lately studied some of the important gen- 
era of the Inarticulate Brachiopods has come to the conclusion that 
the pedicle is a continuation backward of the body-wall of the Brachio- 
pod,’ and thus gives countenance to the suggestion offered many years 
ago by E. Morse, that Lingula, and so the Brachiopods generally were 
related to the Worms, citing the fact that both had red blood. 
Applying Blochmann’s studies on the relation of the pedicle to the 
body-wall in Brachiopoda and regarding the Hyolithide as another 
ancient branch of, or from the worms, one may make the following 
presentation of the general relation of these two types. 



BRACHIOPODA. HYOLITHIDÆ. 
(Ventral Valve). (Tube of Habitation). 
Initial dwelling (| The pedicle, chitinous The larval tube 
often atrophied 4 Calcified apex with diaph-| Apex chambered in several 
or shortened. L ragms in some species 
Visceral { Shell thickened, and rapidly| Shell thickened, and rapidly 
SE Area. expanding expanding 
à = (| Shell thinner, expansion] Shell thinner, expausion of 
2e s | slow, sides sometimes sides retarded 
EME Brachial | parallel 
3 
a s Area. 7 
© | | Front rounded, straight or} Front rounded, straight or 
(| . emarginate emarginate 

The external resemblance of Acrothyra to Hyolithes,? which is car- 
ried out in both valves of the exo-skeleton, has induced the writer to 
make a more extended comparison of the external covering of the body 
in its different parts, to see what proofs there might be of a near 
relationship between them. 
Barrande has figured Hyolithes with the apex downward, Holm in 
his memoir has reversed the attitude of the shell. There is good reason 
to think that the latter is the proper attitude. In sandstone and lime- 
stone beds one so often finds shells of this genus and of Orthotheca 
ensheathed one within the other that it would seem to imply that the 
usual attitude of the living shell was with the mouth of the tube up- 
ward. The decollation of the apex seen in quite a number of species 
would also indicate that absorption of the lower chambers occurred, 
and if these were partly buried in the mud of the sea bottom, one can 
see how this might occur without injury to the occupant of the tube. 


1 Reitrige zur Beurtheilung der Brachiopoden, Fr. Heune 1901. 
? The reference of Hyolithes to the Tube worms and the reasons ‘therefor, 
are given in a previous volume of these Transactions. Trans. Roy. Soc. Can., 
New Ser., Vol. V., Sec. IV., p. 103. 
