524 Forty-fifth Report on the State Museum. 



others median, and again anterior, curving forward in the first 

 case and backward in the last. 



In the non-spiriferous brachiopods, or those in which the 

 brachial apparatus is abbreviated, Ave usually find a simple repre- 

 sentation of the primary lamellae and the jugum which may be 

 variously complicated with the median septum of the brachial 

 valve. In this group the entire calcified apparatus is termed the 

 loop, which is typically composed of two long or short primary 

 or descending lamellce which may recurve more or less profoundly 

 at their anterior extremity [ascending lamellce,) and unite in a 

 transverse band. This last is the homologue of the jugum. In 

 Terebratella, Terebratalia, Muhlfeldtia, Ismenia, and some 

 other genera, the descending lamellae are united to the median sep- 



Fig. 171.— Terebratalia dorsaia. (Woodward.) Fig. 172.— MagasellaCumingi. (Davidson.) 



turn by a dorsal band, which is a residuum resulting from progress- 

 ive resorption of the calcareous parts, and wholly disappears in 

 more advanced forms, such as Magellania venosa. In typical forms 

 of Magellania the septum also has disappeared and the loop in the 

 adult condition is without any evidence of former connection with 

 the valve, except at the hinge-plate. A corresponding adult con- 

 dition is found in the paheozoie genera Cry ptonell a, Meoalanteris 

 Dielasma, etc. In Centronella and Renssklaeria the primary 

 lamellae simply unite at their anterior extremities without reflec- 

 tion, the apparatus here being expanded into a triangular plate. 

 A somewhat similar arrangemenl is seen in Mag as and Platidia, 

 while ill BotJOHARDIA, Kraussina, little is left of the brachial sup- 



7»; 



