228 Reviews — Dr. Bornemann — Cambrian Fossils of Sardinia. 



1878. Girvanella, 'Nicholson and ^th. jun. Probably Rhizopods. 



1885. Strephochetus, H. M. Seeley. Calcareous Sponges. 



1886. Siphonema , 'hoTnemann. Algse allied to living subaerial forms. 

 Whatever may be said in favour of the alliance of this genus to 

 Khizopods, on which the writer is not competent to pronounce an 

 opinion, it is quite certain that it has not the least resemblance to 

 Calcisponges, and its affinity to living subaerial Algae seems very 

 problematical. It is clear, however, that these bodies should retain 

 the generic name first applied to them, and the two later names must 

 be suppressed. 



In the class Spongi93 the author proposes a new genus, Palao- 

 spongia, to include small cylindrical branching bodies, from 1 to 5 mm. 

 in thickness, which in places fill beds of slaty rock, and are exposed 

 in relief on their weathered surfaces. These forms now consist, for 

 the most part, of angular quartz grains ; but it is stated that, in 

 microscopic sections, siliceous spicules arranged parallel with each 

 other to form fibres can be distinctly seen, and between the spicules 

 are grey and dark lines, regarded by the author as indications of the 

 keratose materials of the organism, by which, when in the living 

 state, the spicules were held together ! The genus is regarded as 

 allied to existing monactinellid sponges, and a photograph of a section 

 of the existing Axinella 2Jolypodioides is given to show the resem- 

 blance between it and sections of these Cambrian fossils ! We must 

 confess our inability to perceive this asserted likeness, and we think 

 that the few, scattered, crooked linear bodies shown in the figure, 

 which the author supposes to be spicules, may be otherwise explained. 

 It would indeed be a striking fact, if sponges of this character, which, 

 owing to the fact that their component spicules are only held together 

 by perishable horny material, are of extremely rare occurrence in 

 newer undisturbed strata, should in these disturbed Cambrian rocks 

 be preserved in great abundance. 



The author further states that the forms described by Billings as 

 marine plants, under the name of PalceopJiycus, have a remarkable 

 resemblance to his Palceospongia. In our own opinion the forms 

 known as Palceophyciis, Bill., are most probably the infilled tracks and 

 burrows of marine organisms, and we think that Paltsospongia may 

 have a similar origin. It is to be hoped that, to clear up, if possible, 

 the doubts as to the real nature of this genus, the author will submit 

 his specimens to some one acquainted with the characters of fossil 

 sponges. 



The peculiar cylindrical, cup- or funnel-shaped fossils, of which 

 the genus ArcJiceocyatJiiis, Billings, may be taken as the type, are 

 placed by the author as a distinct class of Coelenterates, in proximity 

 to Sponges, Anthozoa, and the Medusoid Polyps. Fossils of this 

 group are present in great abundance in the massive Cambrian Lime- 

 stones of Sardinia, but they are, for the most part, not well preserved, 

 and can only be studied in microscopic sections. Of these the author 

 prepared a large series, and photographs of them are given in the 

 accompanying plates. 



In addition to ArchceocyatJius, Bill., the author proposes two new 

 genera, Coscinocyathus and Anthomorpha. In the former, regular 



