3?G Geological Society. 



eonsidorahle quantity of ITalimeda ; and Dr. Guppy has described 

 a II (ilimeda-'LimcstonG in the Solomon Islands. Evidence such as 

 this shows that the important deposits of calcareous plant-remains 

 forming at the present day can scarcely be paralleled by any 

 deposit formed in past geological times except, possibly, the lime- 

 stones of the Alpine Trias, which owe their origin to the thallo- 

 phytes D'lplopora and Gijroporella. Among other llalimeda- 

 Limcstones mentioned by the Authors are those of Christmas Island, 

 Fiji and Tonga, and the Xcw Hebrides. The examples from the 

 last-named group are described in detail. They differ considerablj' 

 one from the other in the condition of preservation of their chief 

 organic contents. Chemical and microscopic analyses of the several 

 examples are given. Ilalimechi seems to be more liable to decay 

 than Lithothamnion, corals, or foraminifera, and yet it appears to 

 retain its structure to a considerable depth in reefs. Much of the 

 fine powdery limestone associated with coral-reefs, and more 

 especially with upraised coral-islands, may be primarily due to 

 lagoon and other deposits formed by the agency of Ualimeda. 



2. ' Notes on the Genera Omosjnra, Lopho^pira, and Turritoma ; 

 with Descriptions of New Species.' 13y Miss Jane Donald. 



In a previous paper the Author referred to the researches of 

 Ulrich and Koken among the earlier gasteropoda, and to the groups 

 into which they had divided them. Much knowledge is still 

 required, with regard to their origin and relationships, before really- 

 satisfactory divisions can be made. Tl>e new species described in 

 the paper belong to three genera, characterized by the possession of 

 a band on all the whorls formed by the gradual filling-up during 

 growth of a sinus, and not a slit, in the outer lip. The genera 

 Lophospira, Whitfield, and Turritoma, Ulrich, are not really true 

 Murchisonidte, but are allowed for the present to remain in that 

 family. Ulrich places Omoapira in the family Raphistomidi>?, but 

 it is not a characteristic member, for the whorls are more convex 

 and the spire higher than is the case with the other genera 

 belonging to the family. Ulrich's description is quoted and 

 discussed, and one new species is described from beds of Upper Eala 

 age. Of the genus Lopho^pira, Ulricli's four sections, and sub- 

 sections of certain of these, are discussed. Five new species are 

 referred to the perav rjnlata-?,e(ii\o-a, one new species and one variety 

 to the hicincta-seci'ion, and one species to the rohusta-SQcXion. 

 One new species is described of Turritoma. The specimens dealt 

 with are mainly from the collections of Mrs. Gray, the Sedgwick 

 Museum, the Bristol Museum, and the Geological Survey of 

 Scotland. 



