io TYPE AMMONITES— VII Dec. 



1927 



it indicates whence the genotype should be chosen ; but there are still 

 three specimens, out of which one example is to be selected as the actual 

 standard of reference. Obviously, the one to take is that illustrated 

 in figs. 15, 16. This then now becomes the actual genolectotype of the 

 genus Pcecilomorphus. 



The result is, then, that Ammonites cy chides, d'Orbigny, cxxi, 1, 2, 

 only, is the type of the species, and that Pcecilomorphus cycloides ; 

 S. Buckman, xxn, 15, 16, becomes the genolectotype or standard of 

 reference : it is apparently the same species as d'Orbigny's type. The 

 genotype of Pcecilomorphus, however, should not be quoted as ' Am. 

 cycloides, d'Orbigny'; but as 'Pcecilomorphus cycloides, d'Orbigny sp., 

 as figured by S. Buckman, xxn, 15, 16/ or as ' P. cycloides (d'Orbigny), 

 S. Buckman,' or still shorter as ' P. cycloides ; S. Buckman ' — the semi- 

 colon instead of comma after the trivial name, signifying, as I have 

 suggested before, that the author following is not the original giver of 

 the trivial name. 



It then becomes advisable, for the sake of clarity, to name some of 

 the other forms and some new species. 



P. regulatus, S.B., T.A., PI. DCCXLVI, a compressed form, with 

 regular fine ribs : the largest specimen of the genus which I have seen. 

 Cf. S.B., Mon., xxn, 1, 2, 7, 8, 



P. umbilicatus, nov., d'Orbigny's " variete a ombilic large," Ceph. ; 

 Pal. franc, cxxi, 4, 5, p. 372, Holotype. Like P. regulatus, but more 

 umbilicate. 



P. evolutus, nov., Holotype, S. Buckman, Mon. I. O. Amm., 

 xxn, 21, 22. Like P. umbilicatus, but thinner and barely sulcate. 



P. primiferus, nov. T.A., PL DCCLVI, Holotype, S.B., ex Darell, 

 Coll., No. 4794 ; near Sherborne, Dorset. Cf. P. cycloides ; S.B., Mon. 

 1.0. Amm., xxn, 9, 10. Height of whorl < thickness ; later, height 

 about = thickness ; carinati-bisulcate on rather flattened venter ; 

 costate, with primary ribs distinct, branching into 2 and 3 — primary ribs 

 failing on body-chamber, which is half-a-whorl in length ; umbilicus of 

 moderate width. Proportions, S. 12.25, 45> 53> 2D -5 I 2 3» 39> 4 1 * 2 $- 



It is a peculiarity of examples of Pcecilomorphus that so few show 

 primary ribs. In most of them around the umbilicus the inner lateral 

 area appears as a nearly smooth band — the primary ribs having passed 

 into fine growth-lines which require a lens for detection. These line 

 growth-lines are sometimes entire, sometimes bifurcate. The present 

 specimen and the example cited with it are distinct by showing well- 

 marked primary ribs — hence the name. There is not much difference 

 between the two specimens — the ribs are rather stronger in the T.A. 

 specimen, and there is rather less irregularity in size of ribs on, perhaps, 

 a rather more sulcate, flatter ventral area. 



P. fasciatus, nov., d'Orbigny's " variete a faisceaux," Ceph. ; 

 Pal. franc., cxxi, 3, p. 372. Thick form, strong ribs like bands at 

 intervals. Cf. S.B., Mon., xxn, 17, 18. 



P. asper, nov., Holotype, S.B., Mon., xxn, 3, 4 ; subquadrate 

 whorls, somewhat umbilicate, ribs coarse and rather distant. 



P. inclusus, nov., Holotype, S.B., Mon., xxn, 5, 6 ; broad 

 whorls and a minute umbilicus. 



P. angulinus, nov., Holotype, T.A., DCCLVI I ; subcostate, with 

 an angulate venter ; furrows feeble. 



* P. capillaceus, nov., Holotype, S.B., Mon., xxn, 11, 12 ; small 

 costae, but finishes in the capillate stage. As regards ribbing, more 

 degenerate than P. angulinus, but in respect of venter less so. 



