140 Miscelloneous. 



Segmentation takes place here in the manner stated by Claparede 

 and MecznikofF : the smaller spherules of segmentation grow round 

 the larger ones ; and after complete segmentation an embryo is 

 developed ivitJun the egg-memhrane, bearing a ciliary girdle, and in 

 its anterior part two eye -spots. The posterior end shows a delicate 

 coat of cilia. It now rotates in its capsule like the embryo of a 

 mollusk, until its egg-membrane is absorbed and it can move more 

 freely in the gelatinous envelope. The animal is still quite opaque, 

 when we observe on each side of it two lanceolate setae, and a pad 

 which projects like a handle at the sides and surrounds the animal ; 

 this is the rudiment of the neck-frill. At the formation of the 

 third pair a subulate seta associates itself with the other setae, the 

 neck-pad becomes elongated with the animal, and a more distinct 

 separation between the fore and hind body appears. At the extre- 

 mity of the latter we still observe a band of cilia striking down- 

 wards : and at the cephalic extremity, on which tentacles are now 

 sprouting, we see a small tuft of cilia, which soon falls otf. In other 

 respects I may refer for the further development to Agassiz's de- 

 scription of the process in S. sinrillum, as any thing I could say 

 would be only an unnecessary repetition of what he has said. — 

 Zeitschr. fur wiss. Zool. Bd. xxi. p. 394. 



On presumed American Specimens of Pelomedusa. 

 By Dr. J. E. Gray, F.R.S. (fee. 



The British Museum lately received, along with a collection of fish 

 in spirits, from Dr. Wucherer, from Bahia, a very large specimen 

 of Pelomedusa suhnifa, which is a common South-, East-, and 

 West-African species. Is this another instance of an African tor- 

 toise having colonized, like Kinlxys in South America ? It is 

 considerably larger than any other specimen we have received, but 

 I cannot see that it differs in any other respect. 



Cornalia described a species of Pelomedusa, which is entirely an 

 African genus, under the name of Pentonycc americana; and his 

 description will fit young specimens of this species. He says that it 

 comes from New York. Can that have been from an introduced 

 specimen of P. subrufa brought by the negroes from Africa, as 

 Kiniccys is also supposed to. have been ? 



Note on Trimerella acuminata. By E. Billings. 



The genus Trimerella was founded by me on two species (F.grandis 

 and T. acuminata) ; but of the latter I had only the rostral half of 

 the ventral valve of a small specimen. I therefore named it provi- 

 sionally, and stated that it difi'ered " from T. yrandls in having the 

 spiral extremity much more pointed, and the longitudinal septa 

 running all the way to the beak." (The septa here alluded to are 

 the walls between the tubes mentioned below.) Within the last few 

 -days, Mr. T. C. Weston, of our Survey, discovered several new speci- 



