llv:>tt.] 122 [Aprils. 
forms. This iin|)('rt :iiit f:ict (';inii(it. be too mudi insisted u|)()ii, 
cspeeialh wlicii taken in consideration witli the iiiiiioitaiit dil'fer- 
onees of structui-e thai exist, in these; families. 'I'hey liave not 
onlv the Ini^e siphuuclcs composed of long sef)tal funnels instead 
of tlie short septal funnels of Orthoceras and the riinaining 
Nautiloidea, luit they have the additional primitive more or less 
sei)tate enilosiphnnele and a distinct nepiouic substage. The 
ananepionie shell had a deep, more or less circular or funnel-like 
impression on the apex, whiidi is usually plugged or discontinuous 
internally. The endosipluunde arises from the internal side of 
this involution of the apex, and there is reason to believe that 
there was continuous open connection between the two at an 
early stage, as originally pointed out by Foord in his "Catalogue 
of Hi-itish Cephalopoda." Whether this be so or not, it is 
obvious, according to the standards of classification hei-e adopted, 
that these forms constitute a distinct order of cephalopods. I 
hope siuntly to |)resent tiie evidence for this in detail, having 
already siitlicient on hand to illustrate all the opinions heiv given, 
and I hope to be able to show that the Endosiphonoidea, as I pro- 
pose to call them, are quite distinct in internal structure from true 
Naiitiloidea. 
Whether this be granted or not, it is evident that ;dl observa- 
tions up to the present time show the Endosiphonoidea to have 
been the primitive ancestral or class radical of the Cephalopoda. 
Avhereas Orthoceras is the ordinal radical of its own order and 
also the trunk of the separate diverging orders or lind)s <if the 
ammonoids and belemnoids. 
"liadical" is a very convenient descriptive term and I have 
used it extensively in order to indicate any form that may be 
considered as having given rise to others. Among Brachiopoda, 
Beecher has clearly pointed out that Paterina is a class radical, 
and Jackson that IMiombopteria is a similar class radical in 
Pelccypoda, and Brooks that the Scajdiopoda ai-e very likely the 
subkingdom radical for all classes of Mollusca, or the molluscan 
ra.lical. 
SYNOPSIS. 
Tnti{<>!)U(;ti()N ........ 59-67 
Tenns proposed for tiie four braiu'lics of research, 00; aiixoloj^y or batlunol- 
ogy, 60-67; discussion of terms, GO-61; di-stiuction between growth and 
development, 61 ; Cope's views, 61-62 ; lieredity and growth distinct, 62; Minot's 
