Sonninia and Hammatoceras. 663

mencing the senile stage very early in life. Hamm. anuplectens commences it still earlier

its umbilicus is much more closed, the whole form is more compressed than in Hamm. amaltheiforme, and, in fact, it more truly deserves that trivial name than the species to which it is applied.

Bradford Abbas and Louse Hill, Dorset, are the localities from which my specimens were obtained. The species occurs in the Concavum- zone and is accompanied by Hamm. amaltheiforme, Yacek, Hamm.
climacomphalum, &c.
EXPLANATION OF PLATE XXII.

Fig. 1. Suture-line of a young Pleuroceras pseudocostatum, Hyatt, magnified 4 times.

2. „ Pleuroceras spinatum (Brug.).

3. ,, Pleuroceras subspinatum, S. Buckm.

4. ,, Amaltheus margaritatus, half-grown.

5. „ ,, adult.

6. ,, Sonninia acanthodes, magnified about 4 times.

7. ,, the same, when larger, to compare with fig 1. Natural size.

8. , , Sonnin ia between S. acanthodes and S. adicra adult.

9. „ Sonninia, sp., to compare with fig. 5.

10. „ Sonninia corrugata, Sow., to compare with fig. 5.

11. „ Witcliellia Iceviuscula, Sow., spinous.

12. „ Witchellia, sp.
13. ,, Haugia jug osa (Sow.).
14. ,, Haugia Dumortieri, S. Buckm.
15. ,, Haugia Eseri (Oppel).

16. „ Hammatoceras insigne (Schubler).
17. „ young Hammatoceras dolium, n. sp.

18. „ adult Hammatoceras dolium.

19. „ Hammatoceras planinsigne, Yacek.

20. „ Hammatoceras, sp.

21. „ Erycites fallax (Benecke), a genus allied to Hammatoceras. It shows how the functions of the siphonal lobe have been usurped by an inordinate expansion of the outer portion of the superior lateral lobes. This is a characteristic of Erycites. Note the contrary condition in fig. 5 (see page 656).

22. Inner whorls of Sonninia acanthodes, magnified about 12 times.

23. „ „ „ „ 7 „

Sonninia acanthodes, showing the commencement
of the spines and the carina and sulcations.

24. „ Witchellia Sutneri magnified, to compare with
fig. 22.

25. ,, Amaltheus margaritatus, magnified about 4 times.

Q. J. G. S. No. 180. 3