1920 CARD10CERAS 15 



The topotype is from a band of argillaceous limestone in Oxford Clay, 

 and is not pyritized ; it is iron-stained : judging by the colouring of 

 Sowerby's plate his large example is from the same source. Associated 

 with this specimen — that is from Weymouth — are a large number of 

 similar-looking specimens, all of which are out of clay, are dark black, 

 and are pyritized. They are, presumably, not strictly contemporaries 

 of the example from the band — coming, perhaps, from just above or 

 just below the argillaceous band, or both. They all differ in suture-line —  

 having rather long and narrow lobes : this character may also be noted 

 in the various lamberti-like forms figured by R. Douville from Normandy 

 (Cardioc. 1912). The rarity of Am. lamberti in contrast to the abundance 

 of lamberti-like forms is, perhaps, to be explained by the difference in 

 matrix — that extraction from the limestone band was difficult and 

 subsequent cleaning tedious, whereas the pyritized specimens would be 

 lying out on the surface washed nearly clean. Such attractive specimens 

 would be readily collected, while what looked like the same in bad 

 condition would be neglected. It would be interesting to know if such 

 collection-failure accounts for the absence of Am. lamberti from Normandy 

 or whether it is due to stratal failure. 



Proportions of Am. lamberti, J. Sowerby, 1819, (M.C. Ill, 73, ccxui, 

 3) — T. and F. 63, 43, 24 ? 29 ; of Mr. Tutcher's specimen, S. 69, 43. 5, 

 27.5, 28.5. 



Cardioceras, Neumayr & Uhlig 1881, (Amm. Hilsbild. ; Palaeont. 

 xxvii, (3) III, p. 140). A. Amaltheen mit normaler Lobenzahl . . 2) 

 Loben verzweigt, Antisiphonallobus einspitzig (Cordati) . . Cardioceras 

 nov. gen." No type selected, but " Cardioceras cordatum Sow." given 

 in list of species (p. 141), and this is evidently indicated by the name. 

 Such has been general usage (R. Douville, 1912, 26) ; the other species 

 originally mentioned have long been allocated to other genera. But 

 more precision is required ; for the name Ammonites (or Cardioceras) 

 cordatus has been applied to a whole series of widely-differing forms 

 from several different strata. Therefore Card, cordatum covers various 

 genosyntypes, and a lectotype must be chosen. As Sowerby's holotype 

 of Am. cordatus is a small shell, difficult to identify with accuracy — 

 for a little difference in so small a shell can become a big difference in 

 more fully-grown examples — and as its suture-line is not known, it seems 

 desirable to pass it over in favour of Sowerby's paratype, now well- 

 known from Miss Healey's researches (Pal. U. 1905, 94). The forms 

 to which the name Am. cordatus have been given generally agree more 

 nearly with this than with the holotype. 



". Therefore CARDIOCERAS Neum. & Uhl. 1881, genolectotype Am. 

 cordatus Sowerby, paratype (Min. Conch, 1813, I, p. 51, xvn, 4) = 

 Cardioceras cardia, nom. n., Coll. Brit. Mus. (Nat. Hist.) No. 43980 b. 

 Proportions : T. & F. (Miss Healey), T. 55, F. 43.5, T. 36, T. 29. Tubercu- 

 latum : (ES), for keel is knotted ; (Si). Suture-line (Miss Healey, Pal. U., 

 fig. P.4), EL and L l rather long and about equal, L* short, well separated 

 from guide-line. Keel distinct, bordered by depressed areas, and crossed 

 by V-shaped ribs. " Upper Oxford Clay " [Argovian, c. scarburgense 

 (Argovian 1) ] ; it is about one of the earliest of the carinate Cadoceratids. 

 Loc. " Somersetshire," Sowerby ; " Axminster, Devon," Crick, Types 

 Ceph., Brit. Mus. (N.H.), 1898, 13. I have a recollection of examining 

 this specimen many years ago with the late G. C. Crick, who pointed out 

 some writing on it. This showed "... minster " clearly ; the first 

 part, which was very indistinct, Mr. Crick made out as " Ax " and 

 concluded Axminster, Devon, an impossibility. I now suggest that it is 

 " Sturminster " for Sturminster Newton, Dorset. Specimens in the 



