390 ON A LAEGE MESOZOIC MTTILUS FBOM THE BAECOO, 



and broad. TJmbones terminal small corroded curved. Liga- 

 mental fossa somewhat small, broad terminal shallow, with a long 

 narrow slit for the byssus. Pallial impression long and wedge- 

 shaped. Length 30 centimetres, breadth 19, height 17. Length 

 of hinge depression 9. 



The size and regular shape should distinguish this species. In 

 the lines of growth the younger ones are deep, broad, regular 

 and distinctly margined. The free portions of shelly matter left 

 on the cast show that in spite of its size the testa was not very 

 thick. 



Locality ? Barcoo, Queensland. Horizon ? 



It is impossible to say yet whether the specimen should be 

 referred to the Oolitic or Cretaceous rocks, both of which are 

 known to occur in that locality. Mr. Cha;^. Moore, F.Gr.S., 

 describes three species of Ifi/tilus* but none of them resemble 

 this in the remotest degree in regard to size. In form M. injlatus 

 approaches it, but it is scarcely an inch in length. The rock 

 mass is like that of Wollumbilla in form. I may state that I 

 have a large mass of materials for description, partly derived from 

 the collections of various explorers and partly derived from my 

 own collections of Mesozoic fossils, made during many journeys 

 and explorations in Xorth Queensland. I prefer however to 

 deal with them in one monograph, so that their relative affinities 

 may be perceived. This magnificent species merits an exception 

 because of its size and beauty of form, which so easily distinguish 

 it from all others. For the information of many continental 

 correspondents I append the following observations in Latin : 



MiTiLTJS iNGEXS, 11. s. M. t. oblougo-ovali vel elliptica ; 

 medio tumida vel gibbosa indequc late, regulariter, obscure 

 carinata ; antice depressa postice crassa, baud ponderosa ; 



* Australian Mesozoic Gtiology and Paleontology, Quart, Jour. Geological 

 Soc. Lond. 1870, p. 252. The species described arc M. rtigo-costatus, M. 

 planus, and M. injlatics^ all from Wollunibilla, where Mytilus is said to be 

 abundant on the rocks. 



