390 THE ANATOMY OF VERTEBRATED ANIMALS. 



si^e, and is often denticulated, or comblike, at its free end. 

 The stomach is simple, with the cardiac and pyloric apertures 

 ajiproximated. The ca3cum is long, and has no vermiform 

 appendage. 



In many Lemurs {Stenops, JSTycticehus, Perodicticus, Arcto- 

 celnis, Taivh's) the great arteries and veins of the limbs break 

 up into retia mirabilia formed of parallel branches. 



The ventricles of the larynx may be enlarged, but there 

 are no great air-sacs, such as exist in many other Primates. 



In the brain, the cerebral hemispheres are relatively small 

 and flattened, and have narrow and pointed frontal lobes. 

 They are so short as to leave the cerebellum largely uncovered. 

 The gyri and sulci are scanty, or absent, upon the outer sur- 

 face of the hemispheres, but the internal face exhibits the cal- 

 carine sulcus. The large olfactory lobes project forward be- 

 vond the cerebral hemispheres. 



The pendent penis of the male commonly contains a bone ; 

 tlie testes are lodged in a more or less complete scrotum ; and 

 vesiculffi seminales are generally present. 



In the female, the uterus has two long comua, and the 

 urethra traverses the clitoris. Sometimes there are one or 

 two pairs of teats on the abdomen, in addition to the ordinary 

 pectoral pair. 



The LemuridcB are distinguishable into two families, the 

 Lemurini and the Chelromyini. 



In the Lemurini, the pollex is large, opposable, and almost 

 always has a broad, flat nail. 



The usual dental formula is i. -jr-j c py^.m. m. jtj, or j^^. 



The upper incisors are vertical, and the pairs of opposite 

 sides are generally separated by an interval. The upper 

 canines are large and pointed, and very different from the 

 incisors. The lower incisors are close set, laterally compressed, 

 long and proclivous, and the canines, which resemble them in 

 form and direction, are closely appHed to the outer incisors. 

 When six grinders are present, the anterior three are premo- 

 lars. The anterior premolars, and sometimes all of them, have 

 triangular and sharp-pointed crowns ; the first premolar of the 

 lower jaw, in fact, resembles a canine, but its true nature is 

 shown bv its biting behind the upper canine, not in front of it. 



Very generally the crowns of the upper molars are quad- 

 ricuspidate, and an oblique ridge passes from the antero-ex- 

 ternal to the postero-internal cusp, as in the highest Primates ', 

 while, in tlie lower jaw, there are either two transverse ridges, 



