CONCHOLOGY. 



63 



History, ted. We know, that many of the species are common 

 "•" ~Y~ mm/ to the south coast of England and the shores of the Zet- 

 land Islands. The microscopic species of shells have, 

 since the labours of Boys and Walker, been very suc- 

 cessfully examined by Mr Adams, in the third and 

 fifth volumes of the Transactions of the Linnean Svciety. 

 jordiner, In the year 1788, Cordiner's Remarkable Ruins and 



L7»8. Romantic Prospects of North Britain, appeared in num- 



bers. Several plates of marine vermes are added, with 

 descriptions. But these are too loose and inaccurate to 

 be of any practical utility. Among the plates is a very 

 good figure of Solen Minutus, and several Serpulae. 

 Jerken- Berkenhout published his Synopsis of the Natural 



»out, 1795. History of Great Britain and Ireland, in the year 

 1795. This work contains a very correct list of the 

 British testacea then discovered, 

 'ulteney, In the year 1799> Dr Pulteney's catalogue of the 

 799. shells of Dorsetshire appeared in Hutchinson's new and 



enlarged edition of the history of that country. This 

 catalogue is very valuable, on account of the clear and 

 concise specific characters attached to many of the spe- 

 cies. The figures which he has given of many of the 

 species described by him, are accurate and faithful re- 

 presentations of nature, 

 lonovan, Mr Donovan, whose works on natural history have 

 1799. gained him so much reputation, commenced, in the year 



1799, his work on British Shells, and in the year 1804, 

 five volumes completed the plan. The work contains 

 short descriptions of the different species, with well ex- 

 ecuted figures. The greater number of microscopic 

 shells are excluded ; and what seems a little surprising, 

 no notice is taken of any of the species of the genus 

 Chiton. 

 Montagu. The conchological labours of Mr Montagu are entit- 

 led to the highest praise. His Testacea Britannica ex- 

 hibits innumerable traces of perseverance, observation, 

 and accuracy. In consequence of his situation on the 

 sea-coast, he has had excellent opportunities of exami- 

 ning the animals of shells, which he has embraced. Two 

 parts of his work appeared in 1 803, and a supplement 

 was published in 1 808. The system which Mr Monta- 

 gu follows is decidedly the Linnaean, on which he has 

 endeavoured to make some improvements. He is the 

 first British conchologist who has devoted much at- 

 tention to the contained animals. The species descri- 

 bed are upwards of 470 in number. The figures of the 

 shells contained in thirty plates, are very just represen- 

 tations of nature, and do great credit to the female hand 

 which executed them. 



The descriptive catalogue of British Testacea, insert- 

 ed in the 8th volume of the Linnaean Transactions, is a 

 valuable addition to the British conchologist. It is the 

 joint production of Dr Maton and the Rev. Thomas 

 Rackett. The Linnaean arrangement and terminology 

 are employed throughout. Many obscure species are 

 here admirably elucidated, and the errors of preceding 

 conchologists rectified. 



In the first volume of the Memoirs of the Wernerion 

 Natural History Society, we are presented by Captain 

 Laskey with a list of North British testacea, amounting 

 to 271 species. Some of these are new. To the list is 

 added a plate of well-executed figures. 



TERMS USED IN CONCHOLOGY. 



Explanation of Terms used in the Description of Uni- 

 valves. 



„ The cavity of univalves, or the space which the shell 

 incloses, is, in a few species, divided into hambers, 

 which have a pipe of communication, termed a syphon. 



The base is considered as situated in the external ori- Termino. 

 fice of the shell or mouth, and the opposite extremity of lo gy* 

 the shell is termed the apex, or summit. In the genus n°^~ Y ~™"^ 

 Spirorbis, the base is considered as that portion of the 

 shell which adheres to rocks and sea-weeds. The 

 mouth, in some species, possesses a testaceous lid, or 

 operculum. This lid is generally attached to the organ 

 of motion, and appears to be an instrument of defence. 

 When the animal withdraws itself into the shell, the 

 lid closes the orifice, and secures it from an attack. 

 The edge of the mouth is termed its margin. 



Some shells are simply tubular or conical; but the Whorls, 

 greater part are variously convoluted, the volutions be- 

 ing termed whorls, or spires. These whorls are hi ge- 

 neral visible and distinct, the boundary between each 

 being termed the line of separation. The whorls in 

 some species are simply placed in a lateral position, 

 while in others the whorls are formed upon a pillar, or 

 columella, which runs in the direction of the axis of the 

 shell, the inferior whorl hi this case embracing the su- 

 perior one. The pillar is in some cases nearly solid, in 

 other instances tubular, with its base either open or co- 

 vered. When the base of the tube of the columella is 

 uncovered, the opening is termed the pillar cavity, or 

 umbilicus. 



In general, when a spiral shell is placed upon its base Dextral 

 or mouth, with the apex towards the observer, the shells, 

 mouth will be found situated on the right side, and the 

 whorls will be observed revolving in a direction from 

 right to left, or corresponding with the motion of the 

 sun. These shells are termed dextral. A few species have 

 this order reversed, as the observer will readily perceive. 

 For upon placing the shell in the above-mentioned po- 

 sition, the mouth will be found situated on the left 

 side, and the whorls will revolve from left to right, sinistral 

 These shells are termed sinistral, heterostrophe, or lie- shells. 

 teroclite. 



Several shells are furnished externally with a thin Epidermis. 

 skin, or epidermis. The use of this covering, we have 

 not been able to ascertain. It is common to the other 

 classes of shells also. Some authors have supposed that 

 it secured the shell from being covered with vermes. If 

 this supposition were true, we would not see the Mus- 

 sles, even when very young, overrun with Zoophytes 

 and Balani. 



Explanation of Terms used in the Description of Bi- 

 valves. 



The two sides of bivalves move upon a certain point, Hinge, 

 as a fulcrum, which is termed the hiiige. This part in 

 some shells is smooth, hi others it is furnished with teeth, 

 or small eminences, with which the inner surface of the 

 hinge is set. On each side of the hinge there are usual- 

 ly small projections of the shell, which are denominated 

 beaks, or umbones. These are either reflex, divaricate, 

 or spiral. Near the hinge there is a strong cartilagi- 

 nous membrane, which connects the valves, and which 

 is termed the ligament, under which, and towards the 

 beak, there is usually a groove, called a chink. 



The base of bivalves is considered as situated in the Base, 

 beak. This has been objected to by some conchologists, 

 and the opening or mouth, as in univalves, jiroposed as 

 the proper base. But when we consider the beak as the 

 centre of motion, containing the hinge upon which the 

 valves turn, we feel ourselves justified in retaining the 

 Linnaean definition, or the one already mentioned. The 

 margin of the shell occupies the circumference of the 

 valves and is divided into four parts. The inferior 

 margin, at the margin of the hinge ; the anterior mar- 

 gin, or the margin next to the ligament ; the posterior 



