CARBONIFEROUS FOSSILS OF IRELAND. 103 



Professor Phillips (Palaeozoic Fossils of Devon) has pvoposetl, I believe, the latest important classification of 

 the group before us. His arrangement resembles that of Von Buch. I give it in his own words : 



" Brachiopoda. 



Valves free, attachment by cxserted muscle. 



Valves equal Lingula. 



Valves unequal, larger valve imperforate {Athyrida). 



No cardinal area Producta. 



A cardinal area Calceola. 



Larger valve perforated in or under the beak. 



Perforation reaching to the hinge-line (Delthyrida). 



Cardinal area more or less common to both valves, Orthis. 



Cardinal area confined to the lartjcr valve. 



Internal plates of larger valve separate Spirifera. 



Internal plates of the larger valve united on the mesial line of tlie 

 shell. 



Plates narrow Strigocephalus. 



Plates very broad Pentamerus. 



Cardinal area obsolete ; beak incurved over a minute perforation, 

 which is often obtect, or merely serves to receive the beak of 



the smaller valve Cleiothyris. 



Perforation not reaching to the hinge-line {Cyclothyris). 



Beak truncate, perforate Epithyris. 



Beak acute, the perforation below it Hypotliyris." 



None of the Brachiopoda have a distinct head, eyes, tongue, or any other external organs of sense. They 

 diSer from all the other bivalves, in their shells being symmetrical, one side perfectly resembling the other, and 

 each shell might almost be considered as containing two individuals, socorapletely does this symmetricity extend to 

 the animal : thus, they have two hearts, one on each side ; two circulatory systems, which only meet in the centre, 

 ■where they supply tlie organs of nutrition ; the stomach and intestinal canal occupy the centre of the shell, and 

 are remarkably small ; the muscles are disposed in an equally symmetrical manner ; the foot of other bivalves is 

 replaced in those animals by two long, spirally-rolled, tubular arms ; the iise of these singular organs has been 

 very variously stated. Fischer, of Moscow, took them for the organs of digestion. Pallas and De Blainville 

 considered the fringes with which those arms are provided to be the gills of the animal ; Cuvier opposed this 

 opinion, from having found thegills ofthe genus Lingida on the inner side of the mantle. Miiller (Naturforschen), 

 from an attentive observation of their habits was led to the conclusion that they served the animal for securing 

 its prey ; this is now known to be their true function. They are protruded from the shell by being inflated, or 

 forcibly filled with fluid; when this is efiected, they unroll themselves; the largest, or basal turn, by increasing 

 in diameter, forces open the valves, which have no cartilage, or other contrivance, except this, to keep them 

 open ; and then the delicate extremities, being protruded beyond the edge of the shell, fall into the sea, where 

 they hang until the agitation of the waters bring some little Mollusc within their grasp, when the cause which 

 protruded them being removed, they coil themselves round their prey, and by rapidly retracting to their ori- 

 ginal position, bring the food to the mouth of the animal, which is situated in the centre between them ; the 

 arms retract, from the elasticity ofthe cartilaginous tubes of which they are formed, not by any muscular action. 

 The primary divisions ofthe tribe appear to consist ofthe following families: 1. Delthyridce, or Spirifers; 

 2. the AthyridcB, orProductas; 3. the OrbicuUdce, the Orbiculas ; 4. the Terebratididce, or true Terebratulas ; 

 and 5. the Pentameridce, or chambered Brachiopods. 



It will be seen that I have difiered from the preceding writers by excluding the genus Lingula from the true 



