STEECOEARirS PABASITICUS, PARASITIC JAEGER. 611 



into the large aoterior cavity, the cloaca proper, and the posterior dilatation is nn- 

 nsually well marked by a very prominent projecting ridge or fold of mucons mem- 

 brane. Jnst anterior to this ridge, oq either side, open tiie ureters, and in the male, 

 in close proximity to them, the orihces of the vasa deferentia. The papillae denoting 

 the terminations of these tubes, as well as the orifices themselves, are exceedingly 

 minute and require careful search for their discovery. The posterior dilatation of the 

 cloacal parietes leads through a very narrow canal — a fourth ot an inch or there- 

 about in length — into a well- developed ftursa. This pouch is quite capacious, measur- 

 ing nearly a third of an inch in length by a fourth in breadth. It is of a flattened 

 oval shape, with a rounded free extremity, and in situ lies pretty closely opposed to the 

 posterior wall of the cloaca. 



The superior larynx is small and very simple in structure, being, as usual, merely a 

 flattened conical cavity formed by the plane thyroid cartilage inferiorly, supporting at 

 its anterior extremity the arytenoid cartilages which form the rima glottidis on the 

 superior aspect of the larynx. This aperture is commanded by the ordinary con- 

 strictor and dilator muscles. 



The trachea measures five inches in length from the superior to the inferior larynx. 

 It is, as usual, flattened antero-posteriorly. The compression is more marked near the 

 anterior extremity; the tube becomes more rounded and narrower toward the lower 

 larynx. It is composed of about ninety rings. But few of these rings are of nuilbrni 

 width for the whole of their circumference. They are mostly troader at one point 

 than at another, the narrow part of one being opposite a correspondingly broadened 

 portion of the one next succeeding, so that the inequalities of any two riag 5 mutually 

 correct each other. Along each side of the trachea a quite distinct band of muscular 

 fibres runs the whole length of the tube. 



The cartilage composing the lower larynx is much firmer and denser than that of the 

 upper. The rings of which this portion of the air passage was originally composed 

 are on its posterior aspect still distinctly traceable, but anteriorly the marks of sepa- 

 ration are quite lost, and the surface of the larynx is quite smooth. The shape of the 

 larynx is that of a truncated pyramid, with a subtriangtUar base, whose posterior plane 

 has a concave indentation, and whose anterior edge has become obsolete. Above, the 

 opening of the larynx is a simple flattened oval, similar in shape to the trachea. Be- 

 low it is divided in two by a cartilaginous tTabectdum, which is thrown across from 

 the posterior side to the anterior apex of the base of the pyramid. The shape of tliis 

 septum is such that it forms of the lower apertttre of the larynx two oval openings — 

 the commencements of the two bronchi. 



The bronchi consist of about twenty half rings, their posterior parietes being en- 

 tirely membranous. These rings are slender and of uniform width, the membrane 

 connecting them, and completing the canal posteriorly, being delicate and elastic. 

 They are of about equal length. 



Synampny. — The account of Stercorariua striatug is one of the earliest and an accurate 

 description of this species. The Larus erepidalus of Gmelin and Latham is in all prob- 

 ability based upon the young ; and, if so, has of course priority over pamalorhinus. But 

 the description is short, unsatisfactory, and not diagnostic ; while, being based upon 

 an immature state of plumage, which the Pomarine Jaeger shares -vrith paraiitk-KS. I do 

 not think it advisable to supersede a long and well-known name. The sterujrarius 

 crepidatus of VieiUot is, however, the true parasiticus, as is also the Leitris crej/idatn r t 

 Degland, and of Schinz: bat the Lestris erepidata of Brebm refi^rs to .S. buffoni. ( Vidi: 

 synonyms of these two species.) The only instance I have found of the application of 

 the name j)arasj(ic«« to this species is that of Meyer and Wolf. The rest of the synon- 

 ymy does not require special notice. For a discussion of Catharacta cepphus of Briin- 

 nich see remarks under S. iuffoni. 



STEECOEAPvIUS PARASITICUS, (Briinn.) 



Parasitic Jaeger, 



Lams parasiticus, Lets., Fn. .Snec. .>5 ; >vst. Xat. i, 1766, 226.— Gm., .>Tst. Xat. i 17-- 

 601.— Lath., Ind. Om. ii, 1790. ?i9. 



Catliaraeta paramtica, Bmrsy., Om. Bor. 1764, 37. 



Cataracta parasitica, Eetz.. Fn. .Snec. l^iAi, IbO. 



Caiarractes parasiticus, FuEM., Br. An. 13S. 



Lestris parasitica. In., Prod. 1-11. 273.— TEirw., Man. ii, li20. 79?) (include^ next spe- 

 cies).— Faber, Prod. Isl. Orn. 1->J, 10.5 (both species?;.— BoiE, Isis. l^-.'2. 56J.— 

 Bkehsi, Eur. Vog. ISi*?. 744.— Kaup, Sk. Em. Ear. Thierw. l-2y. 47.— Le->., 

 Tr. Om. 1S31, 616.— SCHixz., Eur. Fn. i, 1^40. .390.— Xacji., V. D. x, l-4i>, .510, 

 pis. •27-2, -273.— Bp., Consp. ii, 1t.56, 205 ; Compt. Eend. xlii, l-.3c;, 7711.— Blas,. 

 J. f O. l-i3.5. 354. 



Lestris parasitica var. coprotheres, Br., Consp. Av. ii, 1656. iOy. 



