Oct. TERMINOLOGY 7 



1919 



the down grade in regard to size. Victoriceras victoris and Tutchericeras 

 perfoliatum are nomomorphs, somewhat reduced, however, in size by the 

 loss of more or less outer whorl, but not so reduced as to be colomorphs. 

 The same applies to the megalomorphs mentioned above : as species 

 these and the oxynotoids are megalomorphs or nomomorphs ; as specimens 

 they are docked or truncated megalomorphs or nomomorphs respectively. 

 D. cylindroides is a nomomorph requiring no qualification ; but the 

 examples of the species usually found are so much reduced that they 

 are colomorphs. 



There seems to be general agreement that the cone-terms initiated 

 by Hyatt, revised and expanded in this work (I, p. xi, II, p. ix) are 

 particularly useful, making for much brevity of expression. Experience 

 shows that some cases of peculiar contour are not properly covered by 

 the terms now in use, and further additions are therefore proposed as 

 follow : — 



Contracticone. The terminal portion of the cone contracts in 

 thickness, not merely to proportionally less than a preceding part, but to 

 actually less. The character is especially marked in certain phaulomorphs, 

 as, for instance, in Trilobiticeras trilobitoides now figured (PI. CXL), which 

 in earlier whorls is a stout cadicone. But it is not confined to phaulo- 

 morphs : it is shown by the nonomorph cadicone Etnileia crater (II, ix). 



It is also a feature of sphsrocones. Of necessity it is a character 

 which requires a reasonably stout whorl for its basis. 



Ellipticone. The regular increasing spiral of the outer edge of 

 the volute is not maintained : it is accelerated and then reduced, making 

 an ovoid or ellipsoid figure. This is shown in the platycone phaulomorphs 

 Cadomoceras cadomense (d'Orbigny) and Cyrtosiceras macrotelus (Oppel). 

 It is also to be observed in sphaerocones of the genus Otoites, and slightly 

 in Sutneria. 



Goniocone. This is an exaggeration of an elliptocone. The 

 outer edge of the conch runs out as if it intended to make a baculicone ; 

 but the inner edge is conservative to the spharocone. The latter tendency 

 prevails, and the outer edge is brought sharply back. The result is a 

 conch with an angle — it is a pointed conch, be it noted, in the direction 

 in which the animal would dart away from an enemy. The typical 

 instance of a goniocone is OJcoptychius refractus (de Haan) of the Callovian. 

 Not quite so gonioconic a form is OZcoptychius grossouvrei Brasil, "Bajocien 

 superieur," Normandy. A similar form (S. B. Coll. 382) has been obtained 

 from Broad Windsor, Dorset, from upper beds of Inferior Oolite (Vesulian, 

 c. truellii or later). 



Dr. A. Morley Davies, whose questions are most stimulating, asks 

 whether it is correct to use the same cone-term for shapes which, though 

 similar, have been arrived at along different routes. Logically it is not ; 

 and such distinction has been carried out in the terms for cone-stages 

 proposed in Vol. I. : an ophiocone and a serpenticone express the same 

 coiled form, but the former is pre- and the latter post-spharoconic. 

 So a sphsrocone developed from a serpenticone, as in the Liparoceratidae, 

 and a spharocone developed from a cadicone, which will presently be 

 shown to be the origin of Labyrinthoceras, are two distinct phenomena. 

 A persistent cadicone, as in the case of various Bajocian Coronates, 

 is very different from the cadicone, with inner whorls platycone, of 

 Cadoceras. But with our present knowledge, or rather, with the back- 

 wardness in the publication of what has been awaiting illustration this 

 many years, it will be inadvisable to attempt too much analysis of terms 

 relating to these subsidiary cycles (Vol. 1, p. xii). It is always possible, 



