Bulletin 47, United States National Museum. 



3. BRANCHIOSTOMA CALIFORNIENSE.* Gill. 



(CALIFORNIA LANCELET.) 



Larger than the other American species, with the muscular bauds in 

 greater number, usually 44 -f 16 + 9 69. Tail very short. Usual length 

 70 mm., or nearly 3 inches. Coast of California, from San Diego Bay 

 southward, very abundant at the mouth of San Diego Bay, where it was 

 first obtained by Dr. J. G. Cooper about 1868; lately taken in large num- 

 bers at San Diego and at San Luis Gonzalez Bay, in the Gulf of California. 

 In specimens from the last-named locality (Albatroso Coll.) the usual for- 

 mula is 45 + 14 4- 9 = 68. 



Branchiosioma, species, COOPER, Cronise, Nat. Wealth California, 489, 1868, San Diego. 

 Branchiostoma calif orniensis, GILL, MS., ANDREWS, I. c., 241, 1893. 



2. ASYMMETRON, Andrews. 



? Epigonichthys^ PETERS, Berl. Monatsber., 327, 1876, (cultellu*). 



Asymmetron, ANDREWS. Studies Biol. Lab. Johns Hopkins Univ., v, 237, 1893, (lucayanum). 



Gonads, or reproductive structures, developed on the right side only. 

 Anal fin without fin rays or successive fin-ray chambers. A long caudal 

 process. Otherwise as in Branchiostoma. One species, (a-cvu/uerpof, 

 wanting symmetry.) 



4. ASYMMETRON LTJCAYANUM, Andrews. 



(BAHAMA LANCELET.) 



Right metapleuron continuous with the median ventral (anal) fin, which 

 passes to the right of the anus. Preoral hood extensive, the cirri united 

 by the membrane throughout the greater part of their length, and smooth, 

 without sensory papillae. Gonads on the right, 29, extending from the 

 15th to the 43d myotomes inclusive. Myotome formula 44 -f- 9 -f- 13 = 66. 

 Length i inch. Adult and young swimming at the surface in the evening 

 in June and July at Bernini and Nassau, Bahamas; also taken buried 

 in calcareous sand. (Andrews.) (Lucayas, the islands discovered by 

 Columbus in 1492, now the Bahamas.) 

 Asymmetron lucayanum, ANDREWS, I. c., 237, 1893, Bernini, Bahamas. 



Class II. MARSIPOBRANCHII.J 



(THE LAMPREYS.) 



Skeleton cartilaginous ; the skull imperfectly developed, not separate 

 from the vertebral column. No true jaws, no limbs, no shoulder girdle, 



* Closely allied to this species is B. elongatum, Sundevall. Myocommata 49 -f 18 + 12 = 79. 

 Length \% to 2% inches. Chinchas Islands, Peru, probably extending northward to Panama, 

 but not yet recorded within our limits. (Sundevall, Olfers. Vet. Akad. Forh., 147, 1853, 

 Chinchas Islands.) 



f Epigonichthys is said to differ from Branchiostoma in the absence of the anal fin. Dr. Andrews 

 states that Mr. Arthur Willey, who has examined its Australian type, E. cidtellus, finds gonads 

 on the right side only, as in Asymmetron. If Asymmetron is a valid genus, probably Epigonichthys 

 Is also valid. It is perhaps distinguishable from Asymmetron by the want of a caudal process. 



J Prof. Cope makes the Marsipobranchii a subclass under a class Agnatha, characterized by the 

 absence of jaws and shoulder girdle. This class is composed chiefly of extinct forms, most of 

 them belonging to the subclass Ostracodermi, and provided with bony dermal plates and lateral 

 limbs. See American Naturalist, October, 1889, 853. The group Marsipobranchii is also often 

 known as Cyclostomi, as Dermopteri, and as Myzontes. 



