1(J2 



PALAEONTOLOGY OF NEW YORK. 



margin of both valves modified lor the passage of the pedicle between them, 

 may take a position near the base of the system, and its elaborate nmscular 

 apparatus may establish it in such a position as a comprehensive type or point 

 of departure for many derivatives. 



n. llin|;fe-teetli of brncliinl valve. 

 h. Hinge-leetli of pediclo-valvc. 

 c. Soniicn-eular i)lalc oi" braclii.-il 



valve. 

 (/. Median lentacle. 

 /. Parietal bands. 

 f/. Botly cavity. 

 h Liver, 



f:. Hepatic chamber of .stomatdi. 

 I. Intestinal chamber of stontach. 

 m. Intcsline. 

 n. Anatj, 

 o. Month. 



p. Muscles (primary). 

 <j. Lophopliorc. 

 r. Posterior unpaired muscle. 

 r. l*alliul sinus. 

 w Its opening into the body cavity. 



Embryonic Stages of Liiii/ida j'yriimhiiitii, Slimpson (= Glotlitlia Amhhurti, Brodcrip). 



ARer Uhooks. 

 Fig. 75. Dorsal view of the youngest larva observed. X 250. 

 Fir. 76. Dorsal view of a somewhat oliler embryo. X -5". 

 Fig. 77. Ventral view of an individual soon after becoming sedentary, nu indicates the edge oltlie larval shell 



The embryological history of Lingola, as elaborated by Brooks,* for L. 

 pyramidata (== Glottidia Audebarti), has an important bearing upon the taxonomic 

 position of this group. The author has shown that the shell in its earlier stages, 

 has a subcircular form, and that the posterior opening for the pedicle is as fully 

 developed on one valve as on the other ; further, that the muscular bands first 

 to appear are a great posterior or umbonal, and two simple transverse bands 

 crossing the interior cavity (but not each other) near the a'sophagus. The lat- 

 ter are regarded by Brooks as representing the muscles h, j, k and /, of the 

 mature animal (see figs. 6, 7, page 10). All these features are apparent in 

 shells of the obolelloids ; the subcircular valves, the pedicle-passage, sometimes 



* Chesapeake Zoological Laboratory ; Scientific Results of Session of 187S. 



