1848.] 47 



4th. Tlie number of yoiing is from six to Ihirteen. I have had a female wiih 

 thirteen in the pouch; never less Xh&nfivr^ 



5th. 'ilie size of the young at birth is four lines in length, two in breadth , 

 weight four grains. 



6th. The structure of the male and female organs has been well described 

 by Cowper, I'l/ron, De Bltinville, Home, and others. But I would remark that 

 there is no communication between the uterine extremity of the lateral tubes (or 

 the sinus, as I would term ii.) and the vagina, as figured by Home and others. 



7th This leads me to mention that parturition takes place as foHoivs: the 

 young pass down tlirough the lateral tubes, there being no other exit for ihem, 

 and immediately after parturitidu these canals are very much enlargerl. 



The mode of transmission to the pouch is a part of the process hitherto un- 

 known, which I have recently witnessed as well as the nature of the circum- 

 stances would permit. The female stood on her hind legs, and ihe body being 

 much bent, the young ap|)eared at the vulva ; they were licked into the pouch. 

 They were born without any trace of an umbilical cord, The pouch was not 

 interfered with for some time, when her mouth was introduced into it while her 

 front paws held it open ; after this manoeuvre was completed, the little ones were 

 all found attached to the teats, I wou'd further remark that this attachment is 

 an instinctive acton their part, as it is impossible to conceive of any interference 

 of the mother effecting it- The mouths of the embryons present but an infinitely 

 small opening, compared w-ith the size of the teat, and with the hand it is an almost 

 impossible attempt to attach them. 



8th. The ova in the vesicles are larger in proportion than in other mammalia; 

 the vitellus is enveloped by a thin vitelline membrane. The germinal vesicle 

 is, however, in the same position as in other mammals; the transformation in the 

 tubes, where I have met with one, after fecundation, appears the same as in the 

 rabbit. In the uterus, the germinal membrane has the same structure and ap- 

 pearance as in the rabbit. I'his stage I witnessed, through Dr. Uachman's kind- 

 ness, as he gave me the uterus to e.xainine. 



9th. Whether these animals be placental or non-placental, is a question which 

 I cannot positively decide until I have finished the series of observations pro- 

 posed, but the inference that they are not placental, is rendered legitimate, first, 

 by the peculiarities in the structure of the brain and other organs, which show 

 their close proximity to the bird ; second, by no allantois attached and conveying 

 blood vessels to the chorion ; third, by the short period of gestation; for the ova 

 were discovered in the uterus on the ninth day, and the period of gestation being 

 fifteen or sixteen days would render such" a structure needless. 



The Committee on Dr. Leicly's description of a new fossil genus of 

 Ruminantoid Pachydermata, reported in favour of publication. 



On a Ni:w Fossil Genus and Species of Riiniinuntoid racliydermata : Merycoido' 



don Cii/hcrfsonii. 



By Joseph Leidy, M. D. 



Meryroidndon.* This genus is founded u[)oii two fragments handed to me by 

 Dr. Morton, who obtained them for the cabinet of the Academy, from Mr. Cul- 



juJjpvxolC^W' rumino ; £1805- forma; ogwi', dens. 



