574 SCIENTIFIC RECORD FOR 1882. 



tion or even any indications of their existence, save in exceptional 

 circumstances. But Mr. Nathorst, of Sweden, has lately been pur- 

 suing certain investigations which may throw some light on their past 

 history, and at the same time serve to explain the nature of certain 

 problematical bodies discovered in the palaeozoic rocks of Scandi- 

 navia. While visiting Oeresund numerous Medusoe of the genus Au- 

 relia were cast ashore with the mouth downwards. "When he took up 

 one he observed that it had sunk in the soft ground by its own weight, 

 and that its gastrovascular system had made a star-like impression," 

 which reminded him of a Cambrian fossil, described as Spatangopsis. 

 "He then followed the matter up further, partly by making impressions 

 of various Medusae and partly by filling up their gastrovascular system 

 with plaster, and so obtained a cast. The preparations thus made cor- 

 responded so exactly in every detail with the problematical bodies from 

 the Cambrian" that no doubt existed as to their analogy. " Tlie stars 

 and pyramids are casts of the gastrovascular systems of the IMedusae, 

 the rays of the stars and the angles of the pyramids correspond with 

 the arms, and the crescent-shaped projections occasionally occurring 

 between the angles are casts of the genital cavities. The impressions 

 on the slabs of rocks are produced by Medusae thrown on the shore, and 

 which, sinking more or less into the soft ground by their own weight, 

 make a more or less complete impression of the body-ca\ity. The 

 bodies lying free in the clay were probably produced by Medusae which 

 lay on their backs, their gastrovascular system becoming filled up with 

 the sand or mud. There are some Medusae which do not swim, but sink 

 into the mud on their backs, and lie still watching for their prey." The 

 "rays" in the fossils vary from four to five. It is urged, however, that 

 even "in the present day individuals are found with five, six, or nine 

 rays," but it is admitted that "certainly this deviation from the normal 

 number appears more frequently in the Cambrian Medusae than in the 

 existing species." In further evidence of the medusoid nature of the 

 Cambrian fossils, it is stated, among other things, that "the impression 

 of the disk and traces of the tentacles are distinctly seen round a four- 

 rayed star on a rock from Lugnas." In fine, the testimony seems to 

 Mr. Nathorst to justify the identification of the fossils in question as 

 true Medusae, and three "species" are considered to be recognizable 

 among those found in the deposits at Lugnas. Inasmuch as the names 

 8pata7igopsis and Astylospongia, which had been proposed for the Cam- 

 brian organisms, were given under a misapprehension as to their rela- 

 tionships and convey misleading ideas, the new Medusites has been pro- 

 posed, and the three species have been designated as M. radiatius (ex 

 Linnarson), M. Lindsiromi (ex Linnarson), and M.favosus (n. sp.). If the 

 alleged facts and conclusions are confirmed, the results of the investi- 

 gation recorded are of unusual interest, as it establishes the contempo- 

 raneity of Medusae with the oldest animals of which we have distinct 

 evidence. (J. E. M. S., (2 II. 326-327), from Handl. K. Svenska Veten- 

 skab Akad., xix. 



