82 PHILOSOPHICAL TRANSACTIONS. [aNNO 1786. 



The 3d shell c, is a very minute, but curious, species of Helix, of a snbco- 

 nical form, consisting of about 5 convex wreaths, gradually diminishing towards 

 . the apex. The colour of the whole shell is brown. Mr. Lightfoot names it 

 Helix spinulusa or tender prickly Helix, and characterises it in the following 

 manner, viz. Helix testa subconica umbilicata, anfractibus quinque convexis, 

 annulis membranaceis acutis cinctis, dorso spinuloso-carinatis, apertura suborbi- 

 culari. 



The shell is umbilicated at the base, and the wreaths are transversely sur- 

 rounded with numerous sharp-edged rings, which are produced in the middle or 

 back of each wreath into a kind of spur, formed of compressed and ver)^- tender 

 spines. It was found at the foot of pales on old bricks and stones, &c, after 

 rainy weather in June and July. 



Fig. 1 , 2, the shell of the natural size, in different positions. Fig. 3, 4, 5, 

 the same magnified. 



The 4th species d, is a Turbo. It strongly resembles the depressed helices, 

 but its circular mouth forbids its being ranked in that Linnean genus. It is of 

 a brown colour, and consists of 4 cylindric or rounded volutions, which are sur- 

 rounded transversely with numerous sharp-edged membranaceous rings, which 

 are very fragile and deciduous; the mouth, when perfect, is bordered with a com- 

 pressed erect margin. Mr. Lightfoot gives the specific character thus, viz. 

 Turbo helicinus. T. testa depresso-plana, hinc umbilicata, anfractibus quatuor 

 torosis, annulis numerosis acutis membranaceis cinctis. Fine ringed turbo. 

 Turbo with depressed-flat shell, umbilicated on one side, with 4 torose wreaths, 

 surrounded by numerous acute membranaceous rings. 



Fig. 1, 2, the shell on both sides, of its natural size. Fig. 3, 4, the same 

 magnified. 



It was found in spring, near Bullstrode, on base stones, &c. 

 The 5 th and last shell, e, is a species of Patella, and is about a quarter of an 

 inch in length, and a tenth of an inch in diameter, having a pointed vertex 

 nearest to the lower end, turned downwards, and leaning to one side. Mr. 

 Lightfoot names it patella oblonga or oblong fresh-water patella, and thus gives 

 its specific character, viz. Patella testa integerrima oblonga compressa membra- 

 nacea, vertice mucronato reflexo obliquo. Patella with perfectly entire, oblong, 

 compressed, membranaceous shell, with reflex, oblique, mucronated vertex. 



It was found in waters near Beaconsfield, adhering to the leaves of the iris 

 pseudacorus. 



Fig. 1 , 2, 3, show it in its natural size, in different positions. Fig. 5, mag- 

 nified, with the vertex upward. Fig. 6, a view of the patella lacustris of Lin- 

 neus, in order to show the plan of the two different species. 



