382 Mejjorts and P.roceedings — 



T. gibbosa, Beck. ; Microsolena expansa, E. & H. ; and Comoseris 

 irradians, E. & H. 



11. " On the Structure and Affinities of the Family Eeceptaculi- 

 tidse, including therein the Genera Ischadites, Murch. ( = Tetragonis, 

 Eichw.), Splicer ospongia, Pengelly, Acantliochonia, g. n., and Becep- 

 tacidites, Defr." By Dr. G. J. Hinde, F.G.S. 



The author's observations have been derived from the study of 

 numerous examples of the family from Silurian and Devonian strata 

 in Devonshire, the West of England, Belgium, Silesia, Bohemia, the 

 isle of Gotland, Canada, and the United States. In an historical 

 sketch the author showed tbat the members of this group have been 

 at various times referred to pine-cones, Foraminifera, sponges, corals, 

 cystideans, and tunicate Mollusca, and that the latest authorities who 

 have written on them consider their systematic position as altogether 

 doubtful. 



The present mineral constitution of these fossils is either of cry- 

 stalline calcite, silica in a secondary condition, iron peroxide, or iron 

 pyrites, or they occur as empty moulds, and from the similarity to the 

 present mineral condition of undoubted siliceous sponges, the author 

 thinks that the Receptaculitidas were also originally siliceous. The 

 skeleton of the members of the group consists of modified hexacti- 

 nellid spicules, in which the summit-ray of the spicule is changed 

 into a rhomboidal or hexagonal plate with the four horizontal rays 

 or arms immediately beneath it, whilst the vertical ray or shaft 

 tapers to a point, and terminates freely in Ischadites and Acantlio- 

 chonia ; in Sphcerospongia it is partially absorbed ; and in Becepta- 

 culites it developes a plate at its distal extremity. The spicular rays 

 are traversed by axial canals, as in other hexactinellid spicules, and 

 these unite in the central point of junction of the rays. The spicules 

 are definitely arranged so that their summit-plates form regularly 

 oblique rows crossing each other, and the horizontal rays radiating 

 and transverse rows. 



The genus Ischadites consists of conical or ovate bodies inclosing 

 a central cloacal cavity with a summit-apertui-e. The basal nucleus 

 or commencement of growth consists of eight small spicules arranged 

 in a circle ; the sp'icule-plates are rhomboidal ; there is no inner 

 plate, as in Beceptacidites. The genus Tetragonis, Eichw., is un- 

 doubtedly congeneric with Ischadites, and, being of later date, be- 

 comes obsolete. Acanthochonia, g. n., resembles Ischadites in spicular 

 structure, but it is open cup-shaped ; it is formed to include a single 

 species, named A. Ban-andei, from Bubowitz, in Bohemia. The genus 

 Sphcerospongia, Pengelly (pars Salter), has hexagonal summit-plates, 

 and the vertical spicular rays are only partially developed. The 

 genus Beceptaculites is cup-shaped ; the spicular plates are rhom- 

 boidal, and the vertical rays develope at their extremities definite 

 plates, which apparently amalgamate into a continuous perforated 

 layer. The author concluded that the Eeceptaculitidge constitute 

 a distinct family of siliceous hexactinellid sponges, whose nearest 

 relationships are to Protospongia, Dictyopliyton, and Plectoderma. 



The genera Cyclocrinus, Eichw. (=Niclidites, Salter), Pasceolus, 



