UNIVALVES. 



PLATE XLIII. 



Genus. PATELLA. 



Character. Shell shaped like a shield, the top pointed, having no spire, the sum- 

 mit sometimes open, and sometimes curved and nodding ; mouth placed at the bot- 

 tom, and widely open. 



Species. 



No. 1. Patella radiata. Shell pointed, acuminate, of a flesh colour streaked 

 with dark red, in the form of rays proceeding from the centre, inside of a 

 pale red colour ; the general design of the ornamental parts is lively in the ex- 

 treme, the rays being joined together and spotted. It is a native of the English 

 coasts, but only found in the deepest and most rocky parts of the beach. 



No. 2. Patella rustica. Shell red, striated closely with protuberant rays, the 

 summit rounded, the inside white, inclining to a pale red. Found in the 

 neighbouring seas and coasts of Gibraltar and of Spain. 



No. 3. Patella cgerulea. 



No. 4. Patella oblonga. Shell brown, within and without, radiated with cen- 

 tral rays, unequally sided, and rather oval in its form ; the outer surface 

 slightly decussated. 



No. 5. Patella adunca. Shell yellow, with fissures, the summit nodding ; 

 mouth red, faintly streaked with brown transversely, the sides unequal, 

 and hollowed out. 



No. 6. Patella cypridium. Shell streaked transversely with gray ; mouth of a 

 pale blue. Found upon the coasts of Scotland and Ireland. 



No. 7. Patella picta. Shell brown without, and blue within, richly striped with 

 dark rays, reaching from the centre. This shell is found upon the African 

 Coast. 



No. 8. 9. Two Patellae of the nodding or incurvated kind, resembling No. 5 in the 

 peculiar form of the top, and, in a small degree, the genus Argonauta, except 

 that they are without the rim. 



REMARKS. 



The genus Patella is perhaps the most simple in its form of all the shells at present known ; 

 it has no twisted spire, and in its exterior shape it is pyramidal and triangular, like the genus 

 Trochus ; its inside is plain and smooth, like the Dentalia and Serpula genera ; it has no 

 chamber or division within, like the Proscenula, which always has a flat stage or projection 

 on the inner and under side; it differs also from the fossil genus described by Lamarck, called 

 the Calyptraea, which has a circular stage placed centrally within. Some of the Patellae have 

 a beautiful satin-like appearance, and a lustre equal or superior to the finest porcelain; these 

 kinds are much valued by the Connoisseurs, and are extremely difficult to represent by any 

 mode of painting ; their excellence must be seen to be fully known ; they are chiefly found in 

 the South Seas, and the warmer regions of the globe. It is curious to consider by what con- 

 trivance of Nature the animal attaches the shell to its body, as one would suppose it would 

 be constantly coming off, by any accident or motion ; but perhaps it may be detained by the 

 power of suction, or by a membrane which can only be detached by the death of the tenant 

 of the small habitation. 



