202 MEMORANDA. 
Notes on Tricuspidaria and Pentastoma.—In the preceding 
number of this ‘ Journal’ (p. 115), a series of clearly defined 
vascular prolongations are describea by me in connexion with 
the calcareous corpuscles of Tricus,.daria. These tubular 
extensions of membrane, though not previously recorded by 
any observer, I have there represented to have been known 
to Professor Van Beneden—an error unintentionally caused 
by the omission of the monosyllable “no” in my MS. It 
should have run thus: “In Professor Van Beneden’s ‘ Vers 
Cestoides’ no mention is made of these tubular extensions in 
the detailed and accurate description of this Cestode there 
iven.’ 
. Since the memorandum referred to was published, I have 
received Van Beneden’s great prize essay, entitled ‘ Mémoire 
sur les Vers Intestinaux ; but the structure of the species 
in question is not there treated at any further length. 
As amore fitting opportunity could not occur, I will also 
mention a peculiarity in respect of the hooks of Tricuspidaria 
which has hkewise escaped notice. I allude to the presence 
of thin chitinous lamin connecting the two lateral horns of 
each hook to the central apophysis. The object of this ar- 
rangement is probably to afford additional security to the 
prong-like processes, thereby rendermg them capable of 

One of the four cephalic hooks of Z'ricuspidaria nodulosa. x 280 diam. 
greater resistance; but whatever other signification or use 
they may possess, their general aspect inevitably reminds one 
of the aortic semilunar valves in the human subject. Van 
Beneden appears to think it an error that the cusps of the 
hooks should have been figured in the ‘Régne Animal’ as 
directed forwards, and has himself, consequently, drawn the 
hooks with the points downwards (‘ Vers Cestoides,’ pl. xxii). 
On referring to the edition of Cuvier’s work, edited by his 
pupils, I find Blanchard’s figure (‘Intestinaux,’ pl. xxxix) 
to indicate an arrangement of the hooks precisely such as I 
have myself seen and figured more than once with the aid of 
a camera; in these cases the cusps were directed forwards. 
It can scarcely be doubted, therefore, that under different 
circumstances the same animal may display the hooks in 
either direction, most probably by inverting and everting 
