CXii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 1 896, 



The Leucosiadjs are small, -well-marked crabs, with rather long 

 chelipeds and a rounded helmet-like carapace, sometimes polished 

 or covered with minute tubercles, the small eyes being inserted 

 deeply and near together on the front of the blunt projecting 

 rostrum : 3 or 4 joints of the abdomen in the female are coalesced 

 into a broadly rounded convex plate, on the inner concave side of 

 which the eggs are carried and concealed. 



The Oxystomata form the first division of the true Brachyura 

 represented in the Cretaceous formation by at least 9 genera, 

 commencing with Necrocarcinus senonensis, Schl., N, Woodwardii, 

 Chalk, Westphalia, and N. tricarinatus, H. Woodw., from the Green- 

 sand; followed by N. avicularis, Fr., and N.perlatus, Fr., from the 

 Chalk of Bohemia : thence we pass on to Orithopsis Bonneyi, Carter, 

 Greensand ; and to Orithya Bechei from the Gault, Folkestone, and 

 0. Woodwardi from the Chalk Marl, Isle of Wight. Trachynotus 

 sulcatus, Greensand, Wiltshire, and Miihracites vectensis, Isle of 

 Wight, with Hemioon Cunningtoni, Greensand, Wiltshire and Cam- 

 bridge, leading on to Eucorystes Carteri, Greensand, Cambridge, 

 Palceocorystes Broderipii and P. StoJcesii, Greensand and Gault, Folke- 

 stone. P. Icevis is from Westphalia ; P. Callianassarum and P. isericus 

 come from the Chalk of Bohemia ; P. Normanii, Bell, from the Chalk 

 Marl, Isle of Wight ; P. Harveyi, H. Woodw., from the Cretaceous of 

 Vancouver Island, and P. Mulleri from the Chalk of Maestricht. 



Passing upward into the Eocene Tertiary we have P. glabra, 

 Eocene, Portsmouth, and Cyclocorystes pulchellus, Bell, London Clay, 

 Holloway ; Mithracia libinioides, Bell, and Campylostcma matuti-' 

 formis, Bell, from the London Clay, Sheppey ; Hepatiscus pulchellus, 

 Bittner, Eocene, Northern Italy, and Egypt ; Calappilia verrucosa, 

 Eocene, Biarritz, and Calappa, sp., Eocene, Hungary ; Typilobus, sp., 

 Eocene, East Indies, and Matuta, sp., Eocene, Hungary. 



In the Miocene and Newer Tertiaries we meet with Atelecyclus, 

 Miocene and Recent; A. rugosus, Miocene, Montpellier; Palceo- 

 myra bispinosa, Miocene, Turin ; Calappa, sp., Newer Tertiary and 

 Recent. Ebalia Bryerii, Leach, Suffolk Crag and Becent ; Leucosia 

 subrliomboidalis and L. cranium, Newer Tertiaries and Recent ; also 

 Ixa tuber culata. post-Tertiary, East Indies. Corystes Cassivelaunus, 

 the Masked Crab, is a recent example of the same family. 



In the OxYRHrNCHA, or ' sharp-snouted ' crabs, represented by 

 Inachus, Maia, Hyas, Stenorliynchus, etc., the carapace is narrow 

 anteriorly and is usually provided with a pointed and bifid rostrum, 

 the hepatic regions of the carapace being small and the branchial 



