216 DR. IIINDE AND ME. HOLMES ON SPOJSTaE-EEMAINS 



secondary spiues. In recent sponges of this genus these flesh- 

 spicules are usually tMcHy set over the surface, forming a dermal 

 crust or layer, as well as scattered through the soft tissues of the 

 sponge. The skeletal spicules of Latrunculia are simple forms 

 of acerates and acuates. 



Previous to the ' Challenger ' Expedition about four or five 

 species with " Sceptrella " spicules had been described, and the 

 ' Challenger ' material yielded four other species. In the Oamaru 

 deposit the sceptrellas are very numerous, and they present an 

 extraordinary variety of form resulting from different modifications 

 of the spined whorls, so that if, judging from the recent sj)onges, 

 only one or at most two of these modifications are present in a 

 species, there must be a greater number of species present 

 in the Oamaru material than have hitherto been found living at 

 the present time. As fossil, Sceptrella spicules were first noticed 

 ia the Jurassic strata of Ilsede, Hanover, by Dr. Eiist (' Pala^on- 

 tographica,' Bd. xxxi. p. 321, pi. xx. figs. 35, 36). 



Latrunculia (a). — PI. XI. fig. 15. Sceptrella Avith short stout 

 shaft terminating at either end with a central prominent conical 

 spine, the base of whicli is surrounded by a ring of obliquely 

 directed spines ; at equal distances on the shaft are two whorls 

 of similar spines projecting directly outwards. All the spines 

 are armed with secondary spines. Length of spicules (including 

 spines) "066 mm., width across whorls '038 mm., thickness of 

 shaft "016 mm. This form is very abundant. It somewhat re- 

 sembles the sceptrella of Latrunculia corticata, Carter (Ann. & 

 Mag. Nat. Hist. s. 5, vol. iii. p. 298, pi. xxvii. fig. 4 a,), but it is 

 twice as large and has the terminal spine in addition. Similar but 

 larger forms are present detached in dredgings by H.M.S. 'Egeria ' 

 from off the S.W. coast of Australia at depths of 3000 fathoms. 

 A verv similar form is also figured by Dr. Eiist from the Jurassic 

 radiolarian marls of Ilsede, Hanover (' Palseontographica,' Bd. xxxi. 

 p. 321, pi. XX. fig. 35). 



Latrunculia (b). — PI. XI. fig. 16. Sceptrella with short thick 

 shaft armed witli short conical spines at the base, above this 

 are two whorls of stout spines apparently rising from the margins 

 of discs, a third whorl is near the summit, and the apex is formed 

 by a group of upwardly directed spines. Length of spicule 

 •05 mm., width across whorls "036 mm., thickness of shaft "0016 

 mm. This spicule is also of the same type as the flesh-spicules 

 in L. corticata, Carter, and in Sce/ptrella regalis, Osc. Sch., but 



