364 Reviews—British Museum Catalogues— 
The introduction contains a most excellent review of the progress 
of research by students of the Cephalopoda, amongst the most able 
of whom are Barrande, Neetling, Zittel, Mojsisovics, Hyatt, and 
Blake, besides many others. | 
To Prof. Hyatt we are indebted for a vast amount of most patient 
and exhaustive research into the origin, structure and modes of 
growth of the cephalopod shell; and whether we agree in whole, or 
only in part, with his views, we cannot but admire the great amount 
of excellent work which he has achieved. Like other primitive 
groups, the Cephalopoda have not escaped the efforts of the embryo- 
logists, who, basing their classification upon the difference in the 
structure of the initial chamber in the Ammonoidea and the Nauti- 
loidea, have placed the former in the Dibranchiata, on the ground 
that the nucleus (protoconch) in the Ammonites agrees with that of 
Spirula, rather than with that of Nautilus. Hyatt however has found 
the shrivelled remains of the protoconch in two species of Orthoceras 
(O. elegans, and O. unguis), which he has figured in “Science” for 
Feb. 1884, p. 126. But the importance of such a character for 
purposes of classification is very doubtful. Indeed, Dr. Zittel has 
well pointed out that no special systematic value has been attached 
to the presence or absence of the embryonic shell (nucleus) in the 
Gasteropoda, which corresponds with the initial chamber of the 
shells of Cephalopoda, and ought to be, and indeed no doubt is, of - 
equal value (Introduction, pp. vii and viii). 
Of course, in the absence of all the soft parts of the animal, 
advantage has to be taken, for purposes of classification, of all the 
various points of structure of the shells of these Paleozoic Molluscs. 
In considering the development of the siphuncle, Professor Hyatt 
has assumed that the ancestral forms of the Cephalopoda had closed 
czeca instead of a siphuncle, and that these were the ‘‘initial stages” 
of the necks of the septa; he further imagines that these ceca, 
“becoming prolonged in descendant forms, were differentiated into 
the funnels, the remnants of the ceca and the thinner walls of the 
sheath proper connecting them were formed by the fleshy siphon. 
This is the condition of the siphon in the typical forms and in the 
tubular-siphoned Orthoceras, but in some aberrant genera [ Hndoceras 
and Piloceras| the fleshy siphon widens near the living chamber, 
becoming conical and forming a sheath. These sheaths lie in the 
large tube formed by the true funnels, and may deposit permanent 
diaphragms as in /ndoceras.” 
Since Hyatt wrote the foregoing, new light has been thrown upon 
this subject by the discovery of the initial chamber of Hndoceras, by 
Dr. Gerard Holm, of Upsala. The enormous size of this chamber, 
which is continuous with the siphuncular cavity, lends countenance 
to Dr. Zittel’s view that the siphuncle was originally a remnant 
of the visceral sac. A similar opinion was enunciated by Dr. H. 
Woodward in his paper “On the Structure of Camerated Shells,” 
in which, after quoting Owen’s statement regarding the connection 
between the Nautilus pompilius and its shell, to the effect that a 
1 «¢Popular Science Review,” 1872, vol. x1. p. 118. 
