1893.] The Menstruation of Semnopithecus entellus. 169 



vertebra, which appear to be not fewer than nineteen, and may have 

 numbered twenty-six. The sacral vertebra are deeply cupped, and the 

 sacral ribs are developed as in Nothosaurus an.6. Pareiasaurus. The sacral 

 ribs form part of the articular face of the first sacral vertebra. The 

 pelvis is imperfectly known ; the ilium is not so extended as in Dicyn- 

 odonts, and conforms to the type of Phocosaurus, which is regarded 

 as Theriodont, The pubis and ischinm are united together on the 

 Dicynodont plan, but are only moderately developed. 



The scapular arch is completely known, and is formed of scapula, 

 coracoid, and pre-coracoid as in Dicynodon and Pareiasaurus. The 

 humerus and bones of the fore limb were relatively short, and only 

 fragments have been preserved which appear to be referable to ulna 

 and radius. 



The hind limb is known from several examples of the femur, which 

 resembles that of Pareiasaurus in the proximal end, but at the distal 

 end is more like the type described as Saurodesmus. 



The tibia is known from its proximal and distal ends ; it has a 

 general resemblance to that of Pareiasaurus, but is more slender. 

 These types are regarded as constituting a distinct group, named 

 Deuterosauria, which is in many respects intermediate between the 

 Placodontia and Theriodontia, but in skull structure appears also to 

 approach Nothosaurs and Plesiosaurs. 



XIV. " The Menstruation of Semnopitkecus entellus!' By 

 WALTER HEAPE, M.A., Balfour Student at the University 

 of Cambridge. Communicated by Professor M. FOSTER 

 Sec, R.S. Eeceived May 16, 1893. 



(Abstract.) 



The specimens used in the following investigation were collected 

 in Calcutta in 1891. 



The phenomena attending menstruation are grouped into four 

 periods, and these are subdivided into eight stages : 



A. Period of rest. Stage I. The resting stage. 



B. Period of growth. Stage 11. The growth of stroma. Stage III. 



The growth of vessels. 



C. Period of degeneration. Stage I Y. The breaking down of vessels. 



Stage V. The formation of lacunae. Stage VI. The rupture 

 of lacunae. Stage VII. The formation of the menstrual clot. 



D. Period of recuperation. Stage VIII. The recuperation stage. 



The body of the uterus consists of an internal mucosa and external 

 muscle layers. The mucosa is composed of uterine and glandular 

 epithelium, blood vessels, a few radial muscles, and stroma. The 



