L. F. Spatii — A ne'W Amononite from Ohdrmoitth. 541 



Specimen 3768 (Coll. W. D. Lang), from the Crumbly Bed, exposed 

 at low spring tides on the floor of Cann Harbour, Golden Cap, repre- 

 sents an impression, on a mass of pyrites, of a shell probably about 

 80 mm. in diameter. At a diameter of 47 mm. the height of the 

 last whorl appears to l)e 30 per cent, and the umbilicus 44 per cent 

 of the diameter. The typical close costation is shown already on the 

 innermost whorls, and may be taken to characterize the specimen 

 sufficiently, but the peripheral ornament is not ])reserved. At 

 the diameter of 10 mm. the last half- whorl sliows about thirty (?) 

 costse. 



Specimen C 18836 (British Museum, Nat. Hist., Dan Haggard 

 Coll.), from near Charmouth (500 yards east of the mouth of the 

 Char River, not found in situ), is preserved in a pyritic concretion 

 which obscures much of the shell and all the inner whorls. The 

 specimen is uncrushed, however, except near the end, and measures 

 about 60 mm. in diameter. Where the last whorl protrudes from 

 the mass of pyrites, at a diameter of 45 mm., the thickness is 21 per 

 cent of the diameter. The ornament is typical and the periphery 

 is particularly instructive in this specimen ; for it shows both the 

 true character of the high, median tubercle, and the sharp points of 

 the ends of the costae ; also the deceptive appearance of the periphery 

 v/here the worn-down ornament produces a rounded ventral area 

 with the flattened costse almost touching the siphonal line. (Com- 

 pare Figs. 2 and 3.) 



The distinctive characters of the new form, as shown by these five 

 specimens, then are : (1) an extremely fine and close costation and (2) 

 a median row of tubercles along the siphonal line, accompanied by two 

 lateral rows of elongated tubercles or ratfier the thickened termina- 

 tions of the cost83. These five specimens are considered to belong 

 to one species, Dayiceras polymorphoides nov. (genotype), the generic 

 name being proposed (on a suggestion from Dr. Lang) to com- 

 memorate the important work of E. C. H. Day on the Lias at 

 Charmouth. 



The last specimen. No. C 18835 (British Museum, Nat. Hist., 

 Dan Haggard Coll.), from about 500 yards east of the mouth of 

 the Char River (not in situ), differs from the other five in having 

 a less close costation, namely, 84 costse on the last whorl shown, as 

 compared with 116 in the type of Dayiceras jMhymorphoides at a 

 similar size. It is preserved in pyrites, but crushed, and has portions 

 of one of the high-zonal Acanthopleurocerates, characteristic of the 

 Pyritic Marls, attached to it. Its diameter is 57 mm. The periphery 

 unfortunately is very imperfect, and the trituberculation is indicated 

 only near the end ; whereas the first half of the outer whorl, owing 

 to the crushing, shows a very thin venter with the ribs apparently 

 meeting at a keel (after the manner of certain carinate Polymorphites 

 or the extreme form of U 2:>tonia jameso7ii figUTed hy llaiig^). It 



1 N. Jahrb. f. Min., etc., 1887, pi. v, fig. 16. 



