50 SOLENODOX PARADOXUS. 



almost straight, posteriorly diverging cerebral margins, instead of the outwardly 

 bowed boundaries seen in Erinaeeus, and Hemicentetes, or the concave outlines 

 of Chrysochloris. The olfactory lobes are more oval, as in Hemicentetes (Leche, 

 :07, p. 102, fig. 87) and the constriction between them and the cerebral hemi- 

 spheres is very shallow in comparison with the condition in the Centetidae. The 

 cerebral lobes do not extend back so far, relatively, as in Centetes, for the opticus 

 and post-o])ticus are visible in dorsal view, as is true also of Erinaeeus. There 

 is a single well marked lateral sulcus on each of the hemis])heres as in the latter, 

 and in addition an ill defined sulcus dorsal to this, which may have been the 

 result of poor preservation. The cerebrum of Centetes is represented as quite 

 smooth. The cerebellum is longer in proportion than in Centetes, but otherwise 

 much similar with a jjrominent vermis bounded posteriorly by a deep notch, 

 and with ])ointed lateral prolongations directed forwards. In median section, 

 directly ventral to the center of the cerebellum, two slight transverse grooves 

 mark off a well defined pyramis and anterior to it a broader pons. 



PLEXUSES. 



The brachial i)lexus (Plate 6, figs. 7, 10) in Sulenodon paradoxus is chiefly 

 made up of trunks from the sixth, seventh, and eighth cervical nerves and the 

 first dorsal nerve. In one individual, a slender filament was present from the 

 base of the fifth cervical nerve passing posteriorly and receiving two minute 

 threads from the sixth cervical nerve. In Solenodon cubanus Dobson found 

 the fifth cervical to enter into the plexus as a major element. More or less 

 variation is to be expected in the details of the arrangement of the nerves, but 

 the chief connections were nearly identical in the specimens examined. The 

 sixth nerve passes distally as a single trunk with a large ixasal branch to the 

 seventh cervical nerve. In one instance this connecting branch had the appear- 

 ance of a fusion of a basal branch from both nerves, but in the other the dual 

 nature of the connection was less clear. The lateral branch of the sixth nerve 

 appears to corresjtond with that supplying tlie suliscapular and teres muscles. 

 The seventh cervical, in addition to the short connection with the sixth, and a 

 similar with the eighth, from the latter of which a common trunk passes off, 

 has a more distal bifurcation, the posterior branch of which unites with a large 

 branch from the eighth cervical. The main portion of the eighth unites with 

 the first dorsal nerve to form a single short trunk, which soon gives off a small 

 posterior branch, the internal cutaneous. The plexus in Solenodon is rather 



