90 MB. S. S. BUCKMAN 0>' [vol. lxxvi, 



are already fully acquainted ; and publication failure * — species 

 have been collected, but have not yet been figured, described, or 

 otherwise given publicity. 



The foregoing remarks will have shown that there are two 

 classes of small ammonites, which may be tabulated as under : — 



I. Ammonites which are small as a matter of growth : these require 



further analysis. 

 II. Ammonites which are small examples with air-chambers, because they 

 have been reduced by geological accidents of deposition, or by 

 accidents of extraction, or by both causes. 



In ' Type Ammonites \" I have proposed a series of technical 

 terms for the different sizes of organisms : — 



Colomorph — small, because reduced by breaking-off of the outer portion 



by geological or artificial agents. 

 Micromorph — small by growth — Hudleston ('Jurassic Gasteropoda' 2 Pal. 

 Soc. 1888, p. 61) subdivided into : — 



Brephomorph — small, because young — baby stage. 



Anamorph — small, because phylogenetically immature. 



Phaulomorph — small, because stunted, but phylogenetically mature. 



Catamorph — small, because phylogenetically degenerate. 

 Nomomorph — of normal or customary size. 

 Megalomorph — of large size — giant stage. 3 



Objection might be taken that these terms are insufficient in 

 number to meet all the requirements which a detailed analysis 

 could show; but for the present argument they should suffice, and 

 a few words may be said to illustrate them. 



The former correlation of the Gloucestershire and Radstock 

 armatum beds mentioned above involved the supposition that the 

 Gloucestershire armati were either colomorphs or phaulomorphs of 

 the Radstock species. They may be colomorphs ; but, not being 

 of the same elate, they would be colomorphs of other species. They 

 are doubtfully phaulomorphs, for such forms are rare in the Lias : 

 they are presumably, being earlier in date, anamorphs — species 

 small because they have not reached their full phylogenetic 

 development. They may be colomorphs of anamorphs — specimens 

 reduced in size geologically or artificially. 



The rarity of phaulomorphs in the Lias — at any rate, until quite a 

 late period — is an interesting fact ; but, now that the phenomenon 

 is recognized, others may be detected. At present there occur to 

 mind the following:— In the Hettangian, Psiloceras hrevieeUatum 



1 See II, 8, pp. 278, 311. 2 II, 9, p. 6. 



3 These terms may help to an understanding of the problem of Rhyncho- 

 nella rostellata and Rh. thalia. The former may not be a dwarf development 

 (a catamorph) of Rh. thalia; but may be a development of the same stock 

 (a phaulomorph of genus Tropiorhyiichia) ; or Rh. thalia may be the megalo- 

 morph of its genus, though not a megalomorph so far as the family (Rhyn- 

 chonellida?) is concerned. At any rate, if Rh. rostellata is not a catamorph 

 of Rh. thalia, it does not need to be later in date: Rh. thalia may be the 

 later. This agrees with the Dorset-Coast evidence — such as it is, and seems 

 to fit the Gloucestershire analysis (Table I, facing p. 70). 



