LIVING BRACIIIOPODA. 341 



How fur tliese various bauds are correlated in the various genera of brachiopods, it is 

 ditficult to determine. In some forms tliey are weakly developed, as for example in 

 Cistella. According to Schulgin, there is no dorsal mesentery in Cistella/ though 

 Kowalevsld states that he has defined it. At the base of the body cavity Schulgin finds 

 that the peritoneum forms an excamtio i)eritonalis, which plays an important part in the 

 circulation of the Ijlood. He also finds the inner surface of the body cavity, as well as 

 the peritonemn, clothed with a low ciliated epithelium. Much further research will be 

 required to ascertain the relation of the various bands and mesenteries. 



Alimentary Tract. 



The alimentary tract, from the mouth to the anus, is very simple. In the Testicar- 

 dines it is straight with the exception of the abrupt dorsal flexure at the anterior portion, 

 and terminates blindly. In Crania it opens posteriorly. In Discinisca it makes a simple 

 turn to the riglit and opens througli the lateral coelomic wall. In the Lingtdidae it ruus 

 straight backward to the posterior wall of the coelomic cavity, then, turning to the left, it 

 runs forward as far as the oljliciue muscles, to turn again, running back dorsally in line 

 with the first segment of the intestine, and then turning to the right, terminates on the 

 right side at a point midway Ijetween the oblique muscles and the anterior occlusor. 

 These various lengths of the intestine are correlated with the size and extent of the 

 coelomic cavity. In the Lingulidae, an elongated cavity permits the intestine to make 

 two turns; in the less capacious cavity of Discinisca the intestine makes but one turn. 

 In the Testicardines, where a remarkable abbreviation of the coelomic cavity is seen, the 

 alimentary tract is concentrated into the smallest possible space ; and in Crania, which has 

 no peduncle and in which the dorsal shell is free around the entire periphery, the 

 intestine terminates posteriorly, the only instance thus far known among living 

 Brachiopoda. In this connection a consideration of the perforation or sometimes simply a 

 notch in the beak of the dorsal shell of many of the fossil genera of Testicardine forms 

 would be of interest.'-^ 



1 Argiope of Kowalevski and Schulgin. 



2 Dr. C. E. Beecher ('92) .says, "The dorsal beaks of Amphigonia, Athyris, Cleiothyris, Atrypa, and Rhynchonella are 

 usually notched or perforate. The perforation come.s from the union of the crural plates above the floor of the beak leaving 

 a passage through to the apex. A similar opening occurs between the cardinal processes in Strophomeua, Stropheodonta, and 

 allied genera, Tnd the chilidium may also be furrowed, as in Leptaena (= Strophomeua) rhomboidalis. This character is 

 evidently in no way connected with the pedicle opening, but points to the existence, in the early articulate genera, of an anal 

 opening dorsal to the axial line, as in the recent Crania. This dorsal foramen was described and figured by King, m 18.50, 

 Hall in 1860, and by several authors since, and has commonly been termed a visceral foramen. 



"Oehlert suggests that it was probably occupied by the terminal portion of the intestine. The persistence of the foramen 

 seems to indicate an anal opening." 



