1^1 



228 mii.LiyriN :!i, unitki) stater national mtseum. 



punctaiiis iiiul larva' ol' Aiiibl.vst(Hiia, In I'lotuiis the sccoiidiiry 

 branches are also present. The librilla" in Siren present dillerent con- 

 ditions, perhaps dependent on the character of their environment as to 

 the abundance of water, etc., and indicating dillerent dejjrees of func- 

 tional elBciency. I have discussed this question under the head of the 

 family Sirenida*. 



The body is rounded, snbquadrate in section, and disi)lays an indis- 

 tinct median <lorsal groove. The transverse j>'rooves are distinct on the 

 sides and nearly meet on the belly, but are not distinct on the back. 

 They vary from thirty-one to thirty-seven in number. The larfjer speci- 

 mens generally have thirty-six and thirty-seven grooves, while smaller 

 ones fre(iuently have only thirty-one and thirty-two. The specimens 

 with thirty-three, thirty-four, and thirty-live arc of medium size ; but a 

 full sized one IVom (Je()rfiia(No.4r);{5) has t]iirty-tw(),and a small one from 

 South Carolina (No. lO.")!!) has thirtv-four. It was on specimens jjresent- 

 iufj- the eharactersof the sujaller indivichmls above mentioned that the.V. 

 iiifeniicdid of Leconte was proposed. I can not distin<:;uish it from the 

 ordinary form. The skin is everywhere i)erfeetly smooth. The tail is 

 comi)ressed from the base to the extremity, and for its distal half is 

 (juite thin. It has a stron,n' dermal liii above and below. It commences 

 above opposite to the anterior extremity of the vent, and below about 

 0!ie-fourth the length of the tail posterior to the vent. 



The branchial fissures, .as remarked in the discussion of the supposed 

 retrograde metamori)liosis of Siren, may be one, two, or three, on one or 

 both sides. In a series of small specimens from South Carolina (No. 

 Mill) the fissures are as follows: L»-l, .'5-2, L»-2, 2-2. In a similar 

 series from CJeorgia (No. b"*,'},")) they are 2-2, 3-3, 2-2 larger than last; 

 2-3 same size as last, and .'5-3 fully grown. 



Measiircmcnls of No. KVll). 



jr. 



Total l.ii-tli 7U 



l,('ii}itli (if licad and lidily 170 



Lcii^'lli to axilla 082 



Liiiiiffli to first l)iaiicliia 0'C> 



\ivun\h to liiu> of caiitlius of nioiilli ()li> 



IiClij;lli to liiu; of cyi' 01 1 



L(!iij»lli of fore-lcfj; from axilla O'Ari'i 



L('iii;tli of ImiiKM'iis from axilla _ 01'.) 



li •iifitli of ciiliitiis (IK) 



Will til hctwcoii nostrils OKi't 



Width lictwt'cii eyes , i}-2:\ 



Width of head ()4ri 



ICxpanso of fore limh.s cxtondnd Ill 



Dt'ptli of tail at middhi (Km 



The general (tolor is a dark lead-color, usually darker above than be- 

 low. There is in sonu' sj)ecimens a yellow band, with irregular or badly 

 delined outline, extending around tln^ miizzh^aiid upper lip lo Ihe base 

 of the antei i(M' braiushia. In some specimens t his band includes tlii' chin ; 



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