18 INFERIOR OOLITE AMMONITES. 



Ludwigia Murcrison-e, var. Baylii, 8. Buclcman. Plate III, figs. 6, 7. 



1878 Ludwigia Muechison^;, Bayle. Explication Carte geol. France, pi. 85, 



fig. 1 only. (Without further detail 

 I am uncertain about the other three 

 figures.) 



Discoid, calcinated, whorls somewhat compressed, ornamented in the young 

 stage with reflexed, bifurcating, rounded ribs, of which the primary are rather 

 coarse. Ribs becoming smaller, and finally losing themselves in lines of growth 

 in adult age. Ventral area without ribs, somewhat flattened, with a distinct 

 rounded keel, not so conspicuous on body-chamber. Inner margin concave, inclu- 

 sion about half the whorl. Mouth border simple, with lateral elongated lappets, 

 and not produced to a point on ventral area. 



The variety L. obtusa has much the same characters, but the primary ribs are 

 coarser, producing spines in the young stage ; the whorls are thicker, narrower, 

 and more quadrangular, the centre is deeper. 



The variety L. Baylii is like the typical form in general, but has very fine ribs, 

 a smaller centre, and is somewhat thinner. 



Ludwigia Murchisonce, is a somewhat variable species. What might be called 

 the middle form was figured by Sovverby, and is consequently the type of the 

 species on each side of which stand these varieties, the one coarser ribbed and thicker, 

 the other finer ribbed and thinner. Quenstedt was the first to give a second or 

 varietal name to L. Murchisonce, when he described as Ammonites Murchisonce. obtusus 

 the specimen figured in his ' Cephalopoden,' pi. vii, fig. 12, and again in his 

 ' Jura,' pi. xlvi, fig. 5. (It should, however, be observed that his Am. Murchi- 

 sonce acutus on this plate has no connection with the true L. Murchisonce, but belongs 

 to the genus Lioceras, being my Lioc. bradfordense to be described presently.) It is 

 this Am. Murchisonce obtusus which Douville raised to specific rank under the name 

 Ludwigia Haugi. But Herr Haug himself, in his pamplet on ' Harpoceras,' page 

 687, thinks that it is merely a variety, and not a species. In this opinion I quite 

 concur, and since this form has long been known as a variety of Am. Murchisonce 

 under the name of obtusus, I have thought it advisable to retain this name. If, 

 however, it had been raised to specific rank, it might probably have been 

 preferable to have retained Douville's name of Haugi. I have also thought it 

 advisable that the opposite variety of L. Murchisonce should be distinguished, 

 and I have consequently proposed the. varietal name Baylii, because of the 

 capital figure of this form given by Bayle in the reference quoted at the heading. 

 It will be found that there is a very slight variation in the suture lines of these 



