SUB-CLASS II HY DROZOA—ACALEPHAE 121 
Under exceptionally favourable conditions, however, as in the Lithographic 
Slates (Upper Jurassic) of Eichstaidt and Solenhofen, impressions of these deli- 
cate organisms are sometimes pre- 
served, which admit of accurate 
systematic determination. 
The best preserved and at 
the same time the most abundant 
speciesis Rhizostomites admirandus, 
Haeckel, belonging to the Acras- 
pedote family of Lhizostomidae. 
Impressions also occur in flinty 
concretions of the Upper Cre- 
taceous, which are most nearly 
referable to the Medusae. Of a 
more questionable nature are the 
organisms occurring in the Cam- 
brian sandstone of Lugnaes, 
Sweden, and described by Torrell 
under the name of Spatangopsis, 
but which Nathorst assigns to the 
Acalephs. In the same strata 
also are found those peculiar 
fucoidal structures known as Rhizostomites admirandus, Haeck. Lithographic slates ; 
Eophyton, which are generally Hee 1/7 natural size. (Missing parts restored 
supposed to be of vegetable 
origin. Nathorst has brought forward evidence, however, to show that these 
may really have been produced by the trails of Jelly-fishes. Here also should 
be noticed the forms described by Nathorst as Medusites, from the Lower 
Cambrian of Sweden, which this author regards as casts of the gastric cavity of 
Jelly-fishes. According to Walcott, similar fossils are common in Alabama.! 

Fie. 216. 
_! Huxley, T., Memoir on the Anatomy and Affinities of the Medusae (Phil. Trans.), 1849.— Aner, 
R., Ueber eine Meduse in Feuerstein (Sitzungsber. Wien. Akad. Bd. LII.), 1865.—Haeckel, #., Ueber 
fossile Medusen (Zeitschr. fiir wissenschaft. Zool. Bd. XV. and XIX.), 1865 and 1870.—Neues Jahrb. 
fiir Mineralogie, 1866.—Jenaische Zeitschr. Bd. VIII., 1874.—System der Medusen, Bd. I. and II., 
Jena, 1880-81.—WNuthorst, A. G., Om Aftryck af Medusor, ete. (K. Svenska Vetensk. Akad. Handl., 
Bd. XIX.), 1881.—Ammon, L. v., Ueber jurassische Medusen (Abhandl. k. baier. Akad. Bd. XVII.), 
1883.— Brandt, A., Ueber fossile Medusen (Mem. Acad. Imp. St. Petersb. vol. XVI., 7th Ser.), 1871. 
—Pohlig, H., Altpermische Medusen (Festschrift zum 70ten Geburtstage R. Leuckarts), 1892.— 
Hall, J., Palaeontology of N.Y., vol. I., 1847, and III., 1859.—20th Report N.Y. State Cabinet 
Nat. Hist., 1868.—Lapworth, C., Notes on British Graptolites (Geol. Mag. X.), 1873.—Hopkinson, J., 
and Lapworth, C., Graptolites of the Arenig and Llandeilo rocks of St. David’s (Quar. Journ. Geol. 
Soe. XXXI.), 1875.—Linnarsson, G., and Nicholson, H. A., On the vertical range of Graptolites in 
Sweden (Geol. Mag. III.), 1876.—Lapworth, C., On Scottish Monograptidae (Geol. Mag. III.), 1876. 
—On the Graptolites of County Down (Ann. Rep. Belfast Nat. Field Club, I., Part IV.), 1877.— 
Haupt, K., Die Fauna des Graptolithen-Gesteins (Neues Lausitzsches Mag. LIV.), 1878.—Kuyser, E., 
In Abhandl. geol. Specialkarte von Preussen II., Heft 4, 1878.—Linnarsson, G., Om Gotland’s 
Graptoliter (Svens. Vet.-Akad. Forh. XXXVI.), 1879.—Lapworth, C., Distribution of the Rhabdo- 
phora (Ann. Mag. Nat. Hist. III.-VI.), 1879-80.—On new British Graptolites (op. cit. V.), 1880.— 
Tullberg, S. A., On species of Didymograptus (Geol. For. Stockholm Férh. V.), 1880.—TZérnquist, 
S. Z., Studier 6fver Retiolites (Geol. For. Stockholm Forh. V.), 1881. Also papers by Tornquist 
and Linnarsson in same volume, pp. 292-326.—Holm, G., Skandinavien’s Graptoliter (Svens. Vet.- 
Akad. Forh. XXXVIII.), 1881.—Tullberg, S. A., Skane’s Graptoliter (Sven. Geol. Undersokn., Ser. 
C., I. and II.), 1882-83.— Spencer, J. W., Graptolitidae of the Upper Silurian System (Bull. Univ. 
Mo. I., and Trans. St. Louis Acad. Sci. IV.), 1884.—Jaekel, O., Ueber das Alter des Graptolithen- 
Gesteins (Zeitschr. deutsch. geol. Gesellsch. XLI.), 1890.—Barrois, C., Mémoire sur la distribution 
des Graptolites en France (Annal. geol. soc. Nord), 1892. 


