THOLADID.E. 



SI 



instninient exists. It is with its rasp-lilie Siliull, 

 covered, as we have seen, with rows of calcareous 

 projections, that the animal w-oiks. "If you ex- 

 amine," says Gosse, "the living shell, 3'oa will see 

 that the fore-part, where the foot protrudes, is set 

 with stony points arranged in transverse and longi- 

 tudinal rows; the former being the result of elevated 

 ridges, radiating from the hinge, the latter that of the 

 edges of successive growths of the shell. These points 

 have the most accurate resemblance to those set on a 

 steel rasp in the blacksmith's shop. It is interesting 

 to know that the shell is preserved from being itself 

 prematurely worn away, by the fact that it is composed 

 of aragonite, a substance much harder than those rocks 

 in which the Pholas burrows. The animal turns in its 

 burrow from side to side when at work, adhering to 

 the interior by the foot, and therefore only partially 

 rotating to and fro. The substance is abraded in the 

 form of a fine powder, which is gradually ejected from 

 the mouth of the hole by contraction of the bronchial 

 syphon." 



The Pholades liave a very extensive range. On 

 both coasts of the Channel they are found in abun- 

 dance, especially the species, Plmhis dactijhis, Pholos 

 crispata, Pholas jvipyracea, and Pliolas melanoitra. 



The Pholailes possess the quality of phosphores- 

 cence, and in the dark emit a peculiarly brilliant liglit. 

 " Those who eat them in an uncooked condition (a not 

 unfrequent circumstance, as the mollusc does not need 

 the aid of cooking to render it savoury), appear in the 

 dark as if they had swallowed phosphorus; and the 

 fisherman who, in a spirit of economy, sups on it in 

 an unlighted chamber, affords to his little ones the 

 amusing spectacle of a fire-eater on a small scale." 



The ravages caused by these alilhyic borers and 

 miners are very considerable. In a geological sense, 

 however, they have an unexpected ulility, for they 

 demonstrate the former levels of the ocean-waters, and 

 show how, in certain places, the sea may have receded 

 from or have gained upon the earth. A remarkable 

 cxim]ile of this strange use of the Pholades, is th.it 

 miniorial of a remote antiquity, the temple of Serapis, 

 situated on the coast of Pozzuoli. 



Pozzuoli, an ancient Cumean colony, the Puteoli of 

 Latin writers, is situated on the Bay of Naples, on its 

 northern shore. Its principal relic of a once splendid 

 past is the temple already referred to — the Serapion 

 or temple of Jupiter Serapis — which, in the course of 

 time had become completely overgrown, and had 

 almost been forgotten, until disinterred by order of 

 Charles III. of Naples, in 1750. 



The building was then found to consist of a q\iadri- 

 lateral abattoir surrounded with chambers, inclosing a 

 circular tem])le in the centre. The court is 140 feet 

 long by 122 feet wide; the main entrance on the S.W. 

 or seaward side, by a doorway of one central and two 

 lateral passages, forming a kind of vestibule, supported 

 by six pilasters. Internally the court was embellished 

 by a portico of forty-eight shapely columns, partly of 

 marble, partly of granite ; beneath which were thirty- 

 two small chambers, sixteen opening upon the court, 

 and sixteen having no apjiarcnt communication with 

 the centre. It is obvious, fjom the remains of stairs. 



still in existence, that there was once an upper story. 

 The chambers in the angles of the N.E. side are twice 

 the dimensions of the others ; they have channels in 

 their walls for the passage of water, and are sur- 

 rounded by marble seats supported by dolphins. 



Between these two spacious chambers the wall of 

 the building is recessed, so as to form a semicircular 

 niche, and in front of this niche stands a pronaos of si-t 

 Corinthian columns and two pilasters, which seem, 

 from the shattered sculpture found in their vicinity, to 

 have anciently supported a richly decorated frieze, and 

 to have been the loftiest portion of the structure. 



Three of the columns are still erect, and are each 

 cut out of a single block of cipollino, 40 feet 3 inches 

 high ; three others lie prostrate and iu fragments cu 

 the ground. 



It is with these three erect columns of cipollino we 

 have here to concern ourselves, for they record a 

 history of physical change in character which, it has 

 been justly said, every one may read, and which no 

 controversy can alter. This history comprises two 

 distinct epochs — one of submergence beneath the 

 ocean-waters, another of elevation above their level. 



If the visitor examines these columns closely he 

 will see that their lower portion, for about twelve feet 

 above the pedestals, has a smooth surface, but shows 

 at different heights unmistakable traces of ancient 

 water-marks. Above this portion, the columns, for 

 about nine feet, are perforated with holes, the work of 

 a species of Pholades — the ifocliola lithojjhaya of 

 Lamarck, according to some authorities. The upper 

 half of the columns is uninjured, except by atmos- 

 pheric influences and the action of the waves. These 

 appearances were at first attributed to an elevation of 

 the sea above its present level — "an hypothesis now 

 known to be untenable, since all the changes on the 

 shores of the Gulf of Naples have been proved to bo 

 local. There is no doubt that the coast of the Bay of 

 liaia has undergone ultimate changes of subsidence 

 and elevation from the date of the foundation of this 

 building." 



From certain inscriptions still extant among the 

 ruins, it is known that the Serapion was used for 

 pagan worship as late as the reign of Septimius 

 Severus. In less than a century after his death, the 

 heathen temples were suppressed by Constantine the 

 Great, and there can be little doubt that it was then 

 abandoned. After this event the ground would 

 appear to have subsided by successive stages — not the 

 level of the sea to have risen— until the lower part of 

 the columns was entirely and permanently submerged. 

 In the twelfth centur}', the eruption of the neighbour- 

 ing Soll'atara seems to have accumulated in the court, 

 to the height of twelve feet, a mass of scoriieand other 

 volcanic matter, which, as the ground sunk down 

 beneath the sea, preserved that portion of the columns 

 from the action of the burrowing Pholades. The sub- 

 sidence continued until the columns were submerged 

 to tlio height of nine feet above this volcaiiic deposit, 

 in which condition they must have undergone the 

 operation of the sea-water for a period of ncarl}' 

 three and a h.alf centuries, while the upper half of the 

 columns rose above the waves. That such was the 



