8 Brachiopoda of the Cincinnati Group. 



covered, like the surface, with microscopic cilise, and exciting currents 

 of pure water over the surface for respiration, the blood being exposed 

 to it in four thick, branching pallial vessels in the lower, and two simi- 

 lar in the small or upper valve ; these great vessels communicate with 

 a vascnilar sinus, ventricle, or heart, on each side of the body, and 

 from the opposite ends of these hearts come the vessels supj^lying the 

 viscera. Dir/estion: the mouth is in the middle, close to the base of 

 the ai-ins, leading (in Terebratula) by a short (esophagus into a wide 

 stomach, surrounded by a liver or group of hepatic follicles; the 

 stomach bending a little, ends in a short, straight intestine (convoluted 

 in Linrjnla), terminating on the right side. Nervous system: a nervous 

 collar, with small ganglionic swellings surrounds the oesophagus, and 

 gives off twigs to the mantle and the adductors." 



The Brachiopoda found in the Cincinnati Group belong to the fol- 

 lowing families: Lingulidce, Craniidce, Discinidce, Rhynchonellidce, 

 Orthidte, and Spirijeridce. 



Family Liugididce — (D'Orb) . 



Arms free, fleshy, inrolled, without shelly supports from the valves, 

 capal>le of being entii'ely protruded beyond the shell, provided with 

 long, firm fimbrite ; valves unconnected by a hinge; pedicle of at- 

 tachment passing out between the beaks of the two valves, neither of 

 wliich are notclied or perforated. Shell corneous,, dense, fibrous, sub- 

 equivalve, equilateral. There is a heart-like vessel on each side, 

 about one third the length from the beak, giving off one large trunk 

 on each side ; the subdivisions of the branchial vessels give off vas- 

 cular loops, arranged as separate lobes of the mantle, resembling the 

 gills of the higher Mollmca, and subservient to respiration ; close to 

 the Ix'ak are the conjoined imprc^ssions in each valve of the posterior 

 pair of muscles ; at aljout one third the length of the shell in front of 

 them are two small, ovate, approximate ovaries, exterior to which are 

 the large impressions of the decussating muscles which produce the 

 sliding motion of the valves on each other. Just in front of the ova- 

 ries are two very large oval lobes of the liver, a third lobe of which is 

 placed in the median line immediately in front of the posterior pair, 

 and is flanked on each side by a rather small, oblique, ovate impres- 

 sion of the anterior pair of adductor muscles in each valve ; consider- 

 ably in front of these, in the median line, are the conjoined, triangular 

 impressions of the anterior pair of muscles, which extend into the 

 ])ediclc at the posterior end. 



This family includes among other genera, the Lingula and Leptobolus. 



