LIVING BKACHIOPODA. 363 



or in L. ItphJuln hut is more fliiring aiul tho riiu is slightly undulating. The body of the 

 nephridiuni is held to the perivisceral wall by a narrow band immediately behind the 

 obliquus internus, and this may ))e a continuation of the ilio-parietal band. A greatly 

 enlarged view of the nephrostome and a portion of the nephridiuni is given in 55 : 2. It is 

 seen to be highly vascular ; large branching lacunae run from the base of the nepln-ostome 

 to the periphery ; these divide, and just before reaching the rim they appear, in the drawing, 

 to be recurved. This appearance is due to the incurving edge of the flaring rim which is 

 very thin and transparent. The lacunae have a delicate light brown tint. The ciliated 

 ridge is seen running in tlie centre of each lacune and tlie blood follows up and down the 

 branches, the current being divided by this ridge. In the undetermined species of 

 Lingida, the neplirostomes were turned towai-d the perivisceral cavity (40: is). Whether 

 during genital activity the nephrostome has the power of turning in this way, is not 

 known. In D. lamellosa (55: 3) the nephridium, while occupying a position similar to that 

 in the Llmjulidae, is fpiite different in its attitude. The nephrostome is turned towards 

 the coelomic cavity and obliquely toward the dorsal shell. It is wide and flaring with 

 regular radiating folds running from the inside nearly to the periphery. It is held to the 

 lateral body wall by a band which seems continuous with the membrane composing the 

 nephrostome. Tliis flaring mouth connects at once with the tubular portion of the 

 nephridium witliout the usual constriction seen in the nephridia of other forms and there 

 is no glandular eidargement or thickening. The tube tapers gradually to its termination 

 in the anterior wall of the coelomic cavity. These openings are seen externally just 

 below the mouth on each side and about midway between the dorsal and ventral parietes. 

 The external openings stand oblique and incline to each other (55 : 4) . A view from 

 within this wall shows that the tubes follow along the ventral floor of the coelomic 

 cavity and then turn upward along the body wall, piercing the wall obliquely (55:5). 

 Externally the openings are as simple as in L. lepidula. In the early stages of D. 

 lamellosa, the nephridium has a long, narrow neplirostome suggesting somewhat the 

 appearance of the same part in Crania as figured Ijy Joubin, though his figure represents 

 the nephrostome as bifurcated. The edge appears to be minutely fringed and the tube 

 shows a slight enlargement in its course (55 : (j) . The small circle associated with the 

 figure indicates the size of the specimen from which the nephridium was drawn. 



We have seen in the Liiu/ulidae a constancy in form and position of the nephridia 

 quite in accordance with those resemblances in structure seen in all the parts. In 

 Discinisca, the nephridia ai'e quite unlike those of the Lhujulklae, as is the animal itself. 

 Crania stands quite apart from all in the form of this organ. In the Testicardine 

 Brachiopoda, the nephridia vary from one another quite as much as does the internal 

 structure of the different forms, or the external appearance of their shells. 



