410 THE LIAS AMMONITES. 



that both represent a similar object. This affords an illustration of the confusion and 

 misunderstanding arising from authors publishing imperfect specimens as types of 

 species, and imparts a lesson to all palaeontologists to exercise the greatest care in the 

 selection of well-preserved examples for figures of new species. If this be not done 

 endless trouble is entailed on those who in after years have to consult plates in original 

 works ; in fact it may be truthfully said that many of the figures of our predecessors 

 are utterly useless and misleading when critically compared with better examples of 

 the objects themselves that have been subsequently discovered. 



This specimen from my collection has much of the thin shell well preserved ; and the 

 deUcate fimbriae on the free side of the numerous annular ribs are all directed obliquely 

 forward, indicating the ornate character of this beautiful Cephalopod when it floated 

 in the Jurassic sea. The whorls are extremely evolute, hence the fragmentary condition 

 in which it is so often found. The penultimate whorl when perfect exhibits four wing- 

 like projections at about equal recurrent intervals in the length of the whorl, the last 

 whorl, which appears to have been the body-chamber of the Cephalopod, has only 

 one of these processes, although they appear to have been developed in the inner 

 whorls. 



Affinities and Differences. — I consider this form to be only a fine-ribbed variety of 

 Lytoceras fimbriatum, and I assume that the shells figured in PI. LXXI and PI. LXXII 

 are the most perfect types of the species. 



Locality and Stratigraphical Position. — I collected this specimen at Lyme Regis from 

 a dark, shaly stratum of the Middle Lias, which readily wasted away when washed 

 in water, but which has since dried up hard and has well preserved my formerly fragile 

 specimen. 



Lytoceras corntjcopia, Youn^ and Bird. PI. LXXIII, figs. 1 — 3. 



Ammonites cobntjcopia, Toung and Bird. Geol. Surv.York.,p. 252, pi. xii.fig. 6,1822. 



— NiTiDus, — Ibid., p. 256, pi. xii, fig. 8, 1828. 



— BALTEATUS, Phillips. Geol. York., pi. xii, fig. 17, 1829. 



— FiMBEiATUs, Simpson. Monogr. Amm., p. 16, 1843. 



— — Zieten. Versteiner. Wiirtemb., p. 16, pi. xii, fig. 4, 1830. 



— — ^roKM. Leth. geognostica, Bcl.I,p. 441,Tf. xxiii, fig. 2, 1837. 



— CORNUCOPIA, d'Orbigny. Paleontol. Fran9aise, Ter. Jurass., torn, i, p. 316, 



pi. 99, 1842. 



— CQRNUcopiiE, Dumortier. Depots Jurassiques du Rhone, partie iv, p. iii, 



pi. xxix, 1874. 



