114 ox THE LITTOR.IL FAUNA OF X. E. AI7STR.VLIA, 



entirely absent. Here and there you meet witli Planaxis, but no 

 JVerita, and Littorina ccenilescenH is quite a different sliell : large, 

 solid, ivory-wliite, witli tbe pur]ile-brown markings of the interior 

 and the rose spots near the moutli very brilliant and distinct. 

 The rock cf the coral reefs is a light-brown mass of coral and 

 coral sand, and for the most part is covered at high water. This 

 may be one of the reasons why there are so few littoral shells. 

 But even on those reefs where a portion of the rock is always 

 uncovered, Siplionaria is nearly the only species that is common, 

 besides oysters. 



There are four or five species of Nerita on the Port Douglas 

 rocks. They are generally congregated together above high 

 water mark in groups of 20 or 30. Nerita costata is the most 

 common. This species is distinguished by its uniform, dull olive- 

 green colour, and its few broad, nearly flat, spiral ribs. It does 

 not seem to vary. On the other hand an equally common one is 

 Nerita ])olita and of this there are endless patterns in its bands, 

 spots, and zigzag markings of black, white, and grey. Nerita 

 grossa is another common form. It is a large, somewhat thin, 

 tumid shell, deeply toothed at the mouth. It may be mistaken 

 for N. costata, with finer ribs and a more elevate spine, but the 

 operculum is quite different. But there is a doubt about the 

 identification of N. costata. It was originally described by Gmelin 

 thus: — '' Shell yellowish within, subglobidar, surrounded with 

 thicker strise, the interstices snowy, both lips toothed, the outer 

 one crenate throughout, inner one sub-convex, wrinkled and 

 tuberculate. Inhabits Nicobar Islands. Shell russet-brown or 

 piceous, crown very obtuse, generally worn and yellowish or 

 white." Born and Chemnitz are quoted for the figures. The 

 latter corresponds with our sheU, and so does the description, 

 except the yeUow interior, which is a variable character. I 

 cannot weU understand how Nicobar Islands can be the habitat 

 and for it not to have been seen at intermediate stations. All 

 the other Neritas of Port Douglas are Linnean shells and were 



