Hyatt.] 25 [May 20, 



Amm. polymorphus mixtus Quenst. is not a synonym of this species? 

 and my remarks are erroneous in this respect. In Quenstedt's col- 

 lection there are several specimens with the Turrilete deformity, sup- 

 posed to be identical with Turr. Valdani and Coynarti. They are, 

 however, members of this species, and not equivalent to Turr. Coy- 

 narti, though perhaps equivalent to Turr. Valdani. 

 ■ Turr. Coynarti is evidently a deformed specimen of planicosta and 

 Turrilites Boblayei, a deformed specimen of carusense, according to 

 D'Orbigny's collection. I have found also similar deformities in sev- 

 eral other species, so that it is an unquestionable deformity to which 

 species of the Lower Lias are more or less susceptible, as previously 

 noticed by Quenstedt. 

 Mieroceras latsecostum. 



Besides the varieties sinuosum and maculatum, this should also 

 include crescens. It cannot readily be separated, either by its form 

 or any of its characteristics. The original of Sowerby has only one 

 row of spines until quite large, when it acquires two. 

 Mieroceras arcigerens. 



This is the English representative of Mieroceras biferum, and in 

 some specimens is not separable from that species, while in others it 

 is* not separable from latcecosta. 



The young of all, and the adult stages of some specimens, are like 

 the young and adult stages* of biferum, while the adult of other speci- 

 mens have the peculiar form and pilse of latcecosta. 

 Deroceras Dudressieri. 



In Quenstedt's collection are several remarkable forms of this 

 species. One begins to show old age, or rather in that case a prema- 

 ture decay of parts begins to take place when the shell is only two 

 inches in diameter. The tubercles and folds begin to show signs of 

 decay in a perfectly normal way, even at this early age. Another 

 specimen from Dewangen (Der Jura, p. 125) has young, with enor- 

 mously large, truncated spinous casts, as in armatum. There are 

 other young of this species which are identified as planicosta Sow. 1 

 Deroceras ziphius. 

 Amm. armatus sparsinodus Quenstedt. 



Quenstedt's magnificent series confirms the views previously 

 printed. 



1 See also Der Jura, p. 97, Capricornus nudus. 



