124 



SCIENCE- GOSSIP. 



GEOLOGY 





conducted by edward a. martin, f.g.s. 



Classification of Fossil Cephalopods. — 

 The cephalopoda constitute a class of molluscs of 

 immense interest to geologists, and well repay close 

 study, since amongst them are classified the nu- 

 merous ammonites and belemnites which are so 

 characteristic of Mesozoic times. The class as a 

 whole is divided into Tetrabranchiata and Di- 

 branchiata. The former include the ammonites 

 and like forms, and survive alone in the pearly 

 nautilus. The latter, the Dibranchiates, include 

 three sub-orders, two of which are found fossil — 

 Belemnoidea and Sepioidea — whilst the third, 

 Octopoda, is very rarely found so in late Tertiary, 

 and includes the living argonaut, the female of 

 which has a delicate, single-chambered, spiral 

 shell. The Belemnoidea are now extinct, except 

 the genus Spirilla, whose internal spiral-chambered 

 shell is found in tropical seas. A complete 

 belemnite consists of three distinct parts : (1) the 

 guard (osselet or rostrum), bearing at its anterior 

 extremity a conical cavity, into which fitted the 

 (2) chambered phragmacone. This is composed 

 of a series of chambers (loculi), and the septa are 

 pierced by the siphuncle. The wall of the phrag- 

 macone is prolonged on the dorsal side into a plate 

 called the (3) proostracurn, and this corresponds 

 to the " pen " of the cuttlefishes. The Sepioidea 

 are plentiful, ranging from Jurassic to the present 

 day. the common cuttlefish (Sepia officinalis) being 

 a well-known species. In this, the proostracurn, 

 or pen, is so developed as to be of equal length 

 with the mantle, and is the cuttle-bone of com- 

 merce. The two other parts which were found in 

 the belemnite are here rudimentary, the chambered 

 phragmacone and the guard being scarcely recog- 

 nisable. There is no siphuncle. Introduced in 

 Triassic times, the Dibranchiates culminate in the 

 Jurassic and Lower Cretaceous, and suddenly de- 

 cline before the commencement of Eocene times. 

 The Tetrabranchiata include the ammonites, the 

 nautilus, orthoceras, ancyloceras, etc., the only 

 surviving form being the pearly nautilus. It 

 comprises two orders, the Nautiloidea and the 

 Ammonoidea. The calcified points of the jaws of 

 these forms of cephalopod are sometimes found 

 fossil in Triassic and Neoeomian strata, and are 

 known as rhyncolites and rhyneotevthis. Apti/cJuis 

 is a name given to Jurassic and Cretaceous fossils 

 which, for a long time undefined, have now come 

 to be regarded as the opercula of ammonoid forms. 

 They consist of two plates, the name wiwupbyckm 

 being given to the fossil when consisting of a single 

 plate only. — E. A. Martin. 



The Eed Crag. — Mr. F. W. Harmer proposes 

 to divide the Red Crag into three divisions — viz. 

 Waltonian, Newbournian, and Butleyan — each 

 being distinguished alike by the difference of their 

 faunas and by the position they occupy. The 

 first, with its southern shells, is confined to the 



county of Essex ; the second, containing fewer 

 southern and extinct, and a larger proportion of 

 northern and recent species, occupies the district 

 between the Orwell and Deben and a narrow belt 

 of land to the east of the latter river : whilst the 

 third, in which Arctic forms like Cardinal groen- 

 landiviim are common, is found only further to the 

 north and to the east. It will thus be seen that 

 these Crag deposits arrange themselves in horizon- 

 tal and not in vertical sequence, assuming always 

 a more boreal and more recent character as they 

 are traced from south to north. They are the 

 littoral accumulations of a sea retreating, not con- 

 tinuously, but at intervals, in a northerly direction. 

 All the beds are believed to have originated in 

 shallow and land-locked bays, successively occupied 

 by the Red dag sea as it retreated northwards, 

 which were silted up one after the other with 

 shelly sand. Mr. Harmer suggests that the con- 

 ditions under which the Red Crag beds originated 

 seem to exist at the present day in Holland, where 

 sandy material brought down by rivers, with dead 

 shells in great abundance from the adjacent sea. 

 is being thrown against and upon the coast, prin- 

 cipally by means of the west winds now prevalent. 

 From meteorological considerations, it seems prob- 

 able that strong gales from the east may have 

 prevailed over the Crag area during the latter part 

 of the Pliocene epoch. Xo other explanation of 

 the accumulation of such vast quantities of dead 

 shells on the East Anglian margin of the North 

 Sea at that period can be suggested. At the pre- 

 sent day the eastern shores of Norfolk and Suffolk 

 are almost destitute of such debris. 



Westow Hill Gravels.— In Science-Gossip 

 of April. 1899, I notice that the plateau or high- 

 level gravel of Westow Hill, Upper Norwood, in 

 Surrey, is referred to on the authority of Prestwich 

 as being but little more than a patch. Recent exca- 

 vations have shown that the gravel is here of con- 

 siderable extent, and in a direction north to south 

 along Church Road it cannot be far short of a mile 

 in length. The following observations were made 

 when electric wires were laid from the top of 

 South Norwood Hill along the Church Road to 

 Upper Norwood. The excavation in which the 

 wires were laid was about four feet deep, but in 

 some places somewhat deeper. From Grange Hill 

 to All Saints' Church there was little or no "soil," 

 the road-material resting upon a sandy loam. 

 Midway between the two was a peculiar patch of 

 pinkish-coloured loam with rounded pebbles. On 

 turning down Church Road orange gravelly loam 

 commenced to prevail, but opposite to the entrance 

 to the churchyard a quantity of green earth was 

 thrown up, containing rounded green-coated flint 

 pebbles. On passing the exit of Upper Beulah 

 Hill the orange gravelly loam again set in. and 

 continued, resembling Croydon gravel. This I have 

 at other times noticed in the same road when 

 excavations have been made for drains, etc., as far. 

 at least, as Westow Street. As the work proceeded 

 in Church Road, from the base to the top of the 

 trench showed a fine dark yellow clayey sand, 

 which from "Northwood" to " St. Ives " contained 

 a large number of rounded flint pebbles. From 

 •• St. Ives " to " Windermere *' the trench was in a 

 pure sand, with scarcely any clayey admixture at 

 all. The cutting continued along Westow Street to 

 Westow Hill, being through an impervious clayey 

 sand, with here and there stones and pebbles. — 

 E. A. Mart in. 



