Report of the State Qeolo* 



52 1 



divisions of the stem of the jugum, or intercalary lamellae, are 

 short, recurving and joining the lateral processes near their 

 union. 



Tins place »»f union of the lateral branches of the jugum is 

 frequently somewhat thickened and expanded i Retzia, Rhyh 

 sriKA, TNciTEsiand inATHTBisit is a broad, saddle-shaped structure. 



FIG.J168 — Brachial apparatus of Koninckina, showing the double spirals. (Bittnek.) 



In the last genus the posterior margin of this saddle is sometimes 

 fimbriated, and not infrequently similar fimbria? or spinules are 

 retained on the outer posterior edges of the primary and second- 



Fig. 1W.— Loop and spiral of Uncites 

 gryphus. (Davidson.) 



Fig. 165.— Portion of spiral of Spiriferina rostroto 

 showing the fimbriae on the outer margins of the 

 coils. (Davidson.) 



ary lamelke; these have also been observed in Atrypa, Ambo- 

 coelia, Dayia, etc. These spinules undoubtedly result from the 

 network of spicules deposited in the cirri of the brachia. 



The jugum is often in close relation with the median septum 

 of the brachial valve. Perhaps in no case among the spire- 

 bearing species is there an actual union of these parts, such as 

 1891. M 73 



