16 On the Cestr -action Philippi (Port Jackson Shark). 



abundance of the true Cestracion fishes in all the Mesozoic 

 Rocks, particularly in the Oolites, and that the only living 

 representative of the family inhabits the Australian Seas, an 

 example of which is now on the table. This specimen was 

 procured in December last, from a fishing station near Mor- 

 dialloc, about fourteen miles from this city, and is called by the 

 fishermen a Groper. From the close proximity of the mouth 

 to the tip of the head it is well calculated for rooting, while 

 the teeth can bruise or grind such Molluscs and Crustacea 

 as may come in its way with facility ; but I should conceive 

 that sea weed would form the principal portion of its food. 



In the same rocks in Europe the Trigonia ( J'rigonos, tri- 

 angular,) abounds ; shells forming a peculiar family (remark- 

 able for the pair of diverging sulcated teeth) ; of which 

 also the only living type is found in our seas. There are 

 only two species of this shell well known, T. Margaritacea 

 and T. Pectinata. The present specimens belong to the 

 Society's collection, and were dredged in the harbour of 

 Port Jackson, New South Wales, in about sixteen feet water, 

 at low tide, from off the tail of a bank leading into deep water ; 

 the bottom was composed principally of dead broken shells and 

 sand, the effect of the under current or drift, mixed with which 

 the Trigonias were found, and could easily be groped out 

 by the shark now under consideration. I believe they are 

 to be met with only in this locality in the harbour. The 

 interior of the shell is highly iridescent Mother-o'-Pearl. 

 They are much prized by collectors. There ar.e upwards of 

 twenty fossil species, but they are not found below the Lias 

 formation. 



Terebratulas, ( Terebratus, bored,) agreeing in generic cha- 

 racter with the living Australian ones, also abound in the 

 Oolite Rocks of Europe, but are not so interesting as the 

 above, because examples (though rare) are found in the seas 

 of all parts of the world, and in all the rock formations from 

 the Silurian to the Tertiary inclusive. 



The specimens before you were also procured in the har- 

 bour of Port Jackson, from under rocks on the borders of 

 the harbour, by inserting the arm into the cavities, where 

 they can be detected hanging by a short fleshy tendon 

 passing through the hole in the larger and upper valve. I 

 mention this fact from the circumstance that Lamarck and 

 others consider that, from the locality of the Fossil species of 

 this genus, these shells may be presumed to inhabit the sea 

 at a great depth; and Professor Owen remarks that the 



